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Chapter 10
Imaginary Journeys: The Lojban Space/Time Tense System

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1. Introductory

This chapter attempts to document and explain the space/time tense system of Lojban. It does not attempt to answer all questions of the form ``How do I say such-and-such (an English tense) in Lojban?'' Instead, it explores the Lojban tense system from the inside, attempting to educate the reader into a Lojbanic viewpoint. Once the overall system is understood and the resources that it makes available are familiar, the reader should have some hope of using appropriate tense constructs and being correctly understood.

The system of Lojban tenses presented here may seem really complex because of all the pieces and all the options; indeed, this chapter is the longest one in this book. But tense is in fact complex in every language. In your native language, the subtleties of tense are intuitive. In foreign languages, you are seldom taught the entire system until you have reached an advanced level. Lojban tenses are extremely systematic and productive, allowing you to express subtleties based on what they mean rather than on how they act similarly to English tenses. This chapter concentrates on presenting an intuitive approach to the meaning of Lojban tense words and how they may be creatively and productively combined.

What is ``tense''? Historically, ``tense'' is the attribute of verbs in English and related languages that expresses the time of the action. In English, three tenses are traditionally recognized, conventionally called the past, the present, and the future. There are also a variety of compound tenses used in English. However, there is no simple relationship between the form of an English tense and the time actually expressed:

I go to London tomorrow. I will go to London tomorrow. I am going to London tomorrow.
all mean the same thing, even though the first sentence uses the present tense; the second, the future tense; and the third, a compound tense usually called ``present progressive''. Likewise, a newspaper headline says ``JONES DIES'', although it is obvious that the time referred to must be in the past. Tense is a mandatory category of English: every sentence must be marked for tense, even if in a way contrary to logic, because every main verb has a tense marker built into to it. By contrast, Lojban brivla have no implicit or explicit tense marker attached to them.

In Lojban, the concept of tense extends to every selbri, not merely the verb-like ones. In addition, tense structures provide information about location in space as well as in time. All tense information is optional in Lojban: a sentence like: 

1.1)	mi klama le zarci
	I go-to the market.
can be understood as:

I went to the market. I am going to the market. I have gone to the market. I will go to the market. I continually go to the market.
as well as many other possibilities: context resolves which is correct.

The placement of a tense construct within a Lojban bridi is easy: right before the selbri. It goes immediately after the ``cu'', and can in fact always replace the ``cu'' (although in very complex sentences the rules for eliding terminators may be changed as a result). In the following examples, ``pu'' is the tense marker for ``past time'': 

1.2)	mi cu pu klama le zarci
	mi pu klama le zarci
	I in-the-past go-to the market.
	I went to the market.
It is also possible to put the tense somewhere else in the bridi by adding ``ku'' after it. This ``ku'' is an elidable terminator, but it's almost never possible to actually elide it except at the end of the bridi: 

1.3)	puku mi klama le zarci
	In-the-past I go-to the market.
	Earlier, I went to the market.

1.4)	mi klama puku le zarci
	I go-to in-the-past the market.
	I went earlier to the market.

1.5)	mi klama le zarci pu [ku]
	I go-to the market in-the-past.
	I went to the market earlier.
Examples 1.2 through 1.5 are different only in emphasis. Abnormal order, such as Examples 1.3 through 1.5 exhibit, adds emphasis to the words that have been moved; in this case, the tense cmavo ``pu''. Words at either end of the sentence tend to be more noticeable.

2. Spatial tenses: FAhA and VA

The following cmavo are discussed in this section: 

	vi	VA	short distance
	va	VA	medium distance
	vu	VA	long distance

	zu'a	FAhA	left
	ri'u	FAhA	right
	ga'u	FAhA	up
	ni'a	FAhA	down
	ca'u	FAhA	front
	ne'i	FAhA	within
	be'a	FAhA	north of
(The complete list of FAhA cmavo can be found in Section 27.)

Why is this section about spatial tenses rather than the more familiar time tenses of Section 1, asks the reader? Because the model to be used in explaining both will be easier to grasp for space than for time. The explanation of time tenses will resume in Section 4.

English doesn't have mandatory spatial tenses. Although there are plenty of ways in English of showing where an event happens, there is absolutely no need to do so. Considering this fact may give the reader a feel for what the optional Lojban time tenses are like. From the Lojban point of view, space and time are interchangeable, although they are not treated identically.

Lojban specifies the spatial tense of a bridi (the place at which it occurs) by using words from selma'o FAhA and VA to describe an imaginary journey from the speaker to the place referred to. FAhA cmavo specify the direction taken in the journey, whereas VA cmavo specify the distance gone. For example: 

2.1)	le nanmu va batci le gerku
	The man [medium distance] bites the dog.
	Over there the man is biting the dog.
What is at a medium distance? The event referred to by the bridi: the man biting the dog. What is this event at a medium distance from? The speaker's location. We can understand the ``va'' as saying: ``If you want to get from the speaker's location to the location of the bridi, journey for a medium distance (in some direction unspecified).'' This ``imaginary journey'' can be used to understand not only Example 2.1, but also every other spatial tense construct.

Suppose you specify a direction with a FAhA cmavo, rather than a distance with a VA cmavo: 

2.2)	le nanmu zu'a batci le gerku
	The man [left] bites the dog.

Here the imaginary journey is again from the speaker's location to the location of the bridi, but it is now performed by going to the left (in the speaker's reference frame) for an unspecified distance. So a reasonable translation is:

To my left, the man bites the dog.

The ``my'' does not have an explicit equivalent in the Lojban, because the speaker's location is understood as the starting point.

(Etymologically, by the way, ``zu'a'' is derived from ``zunle'', the gismu for ``left'', whereas ``vi'', ``va'', and ``vu'' are intended to be reminiscent of ``ti'', ``ta'', and ``tu'', the demonstrative pronouns ``this-here'', ``that-there'', and ``that-yonder''.)

What about specifying both a direction and a distance? The rule here is that the direction must come before the distance: 

2.3)	le nanmu zu'avi batci le gerku
	The man [left] [short distance] bites the dog.
	Slightly to my left, the man bites the dog.

As explained in Section 1, it would be perfectly correct to use ``ku'' to move this tense to the beginning or the end of the sentence to emphasize it: 

2.4)	zu'aviku le nanmu cu batci le gerku
	[Left] [short distance] the man bites the dog.
	Slightly to my left, the man bites the dog.

3. Compound spatial tenses

Humph, says the reader: this talk of ``imaginary journeys'' is all very well, but what's the point of it? --- ``zu'a'' means ``on the left'' and ``vi'' means ``nearby'', and there's no more to be said. The imaginary-journey model becomes more useful when so-called compound tenses are involved. A compound tense is exactly like a simple tense, but has several FAhAs run together: 

3.1)	le nanmu ga'u zu'a batci le gerku
	The man [up] [left] bites the dog.
The proper interpretation of Example 3.1 is that the imaginary journey has two stages: first move from the speaker's location upward, and then to the left. A translation might read:

Left of a place above me, the man bites the dog.
(Perhaps the speaker is at the bottom of a manhole, and the dog-biting is going on at the edge of the street.)

In the English translation, the keywords ``left'' and ``above'' occur in reverse order to the Lojban order. This effect is typical of what happens when we ``unfold'' Lojban compound tenses into their English equivalents, and shows why it is not very useful to try to memorize a list of Lojban tense constructs and their colloquial English equivalents.

The opposite order also makes sense: 

3.2)	le nanmu zu'a ga'u batci le gerku
	The man [left] [up] bites the dog.
	Above a place to the left of me, the man bites the dog.
In ordinary space, the result of going up and then to the left is the same as that of going left and then up, but such a simple relationship does not apply in all environments or to all directions: going south, then east, then north may return one to the starting point, if that point is the North Pole.

Each direction can have a distance following: 

3.3)	le nanmu zu'avi ga'uvu
		batci le gerku
	The man [left] [short distance] [up] [long distance]
		bites the dog.
	Far above a place slightly to the left of me,
		the man bites the dog.
A distance can also come at the beginning of the tense construct, without any specified direction. (Example 2.1, with VA alone, is really a special case of this rule when no directions at all follow.) 

3.4)	le nanmu vi zu'a batci le gerku
	The man [short distance] [left] bites the dog.
	Left of a place near me, the man bites the dog.
Any number of directions may be used in a compound tense, with or without specified distances for each: 

3.5)	le nanmu ca'uvi ni'ava
		ri'uvu ne'i
		batci le gerku
	The man [front] [short] [down] [medium]
		[right] [long] [within]
		bites the dog.
	Within a place a long distance to the right
		of a place which is a medium distance downward
		from a place a short distance in front of me,
		the man bites the dog.

Whew! It's a good thing tense constructs are optional: having to say all that could certainly be painful. Note, however, how much shorter the Lojban version of Example 3.5 is than the English version.

4. Temporal tenses: PU and ZI

The following cmavo are discussed in this section: 

	pu	PU	past
	ca	PU	present
	ba	PU	future

	zi	ZI	short time distance
	za	ZI	medium time distance
	zu	ZI	long time distance
Now that the reader understands spatial tenses, there are only two main facts to understand about temporal tenses: they work exactly like the spatial tenses, with selma'o PU and ZI standing in for FAhA and VA; and when both spatial and temporal tense cmavo are given in a single tense construct, the temporal tense is expressed first. (If space were expressed before time, then certain constructions would be ambiguous.) 

4.1)	le nanmu pu batci le gerku
	The man [past] bites the dog.
	The man bit the dog.
means that to reach the dog-biting, you must take an imaginary journey through time, moving towards the past an unspecified distance. (Of course, this journey is even more imaginary than the ones talked about in the previous sections, since time-travel is not an available option.)

Lojban recognizes three temporal directions: ``pu'' for the past, ``ca'' for the present, and ``ba'' for the future. (Etymologically, these derive from the corresponding gismu ``purci'', ``cabna'', and ``balvi''. See Section 23 for an explanation of the exact relationship between the cmavo and the gismu.) There are many more spatial directions, since there are FAhA cmavo for both absolute and relative directions as well as ``direction-like relationships'' like ``surrounding'', ``within'', ``touching'', etc. (See Section 27 for a complete list.) But there are really only two directions in time: forward and backward, toward the future and toward the past. Why, then, are there three cmavo of selma'o PU?

The reason is that tense is subjective: human beings perceive space and time in a way that does not necessarily agree with objective measurements. We have a sense of ``now'' which includes part of the objective past and part of the objective future, and so we naturally segment the time line into three parts. The Lojban design recognizes this human reality by providing a separate time-direction cmavo for the ``zero direction'', Similarly, there is a FAhA cmavo for the zero space direction: ``bu'u'', which means something like ``coinciding''.

(Technical note for readers conversant with relativity theory: The Lojban time tenses reflect time as seen by the speaker, who is assumed to be a ``point-like observer'' in the relativistic sense: they do not say anything about physical relationships of relativistic interval, still less about implicit causality. The nature of tense is not only subjective but also observer-based.)

Here are some examples of temporal tenses: 

4.2)	le nanmu puzi batci le gerku
	The man [past] [short distance] bites the dog.
	A short time ago, the man bit the dog.

4.3)	le nanmu pu pu batci le gerku
	The man [past] [past] bites the dog.
	Earlier than an earlier time than now,
		the man bit the dog.
	The man had bitten the dog.
	The man had been biting the dog.

4.4)	le nanmu ba puzi batci le gerku
	The man [future] [past] [short] bites the dog.
	Shortly earlier than some time later than now,
		the man will bite the dog.
	Soon before then, the man will have bitten the dog.
	The man will have just bitten the dog.
	The man will just have been biting the dog.
What about the analogue of an initial VA without a direction? Lojban does allow an initial ZI with or without following PUs: 

4.5)	le nanmu zi pu batci le gerku
	The man [short] [past] bites the dog.
	Before a short time from or before now,
		the man bit or will bite the dog.

4.6)	le nanmu zu batci le gerku
	The man [long] bites the dog.
	A long time from or before now,
		the man will bite or bit the dog.
Example 4.5 and Example 4.6 are perfectly legitimate, but may not be very much used: ``zi'' by itself signals an event that happens at a time close to the present, but without saying whether it is in the past or the future. A rough translation might be ``about now, but not exactly now''.

Because we can move in any direction in space, we are comfortable with the idea of events happening in an unspecified space direction (``nearby'' or ``far away''), but we live only from past to future, and the idea of an event which happens ``nearby in time'' is a peculiar one. Lojban provides lots of such possibilities that don't seem all that useful to English-speakers, even though you can put them together productively; this fact may be a limitation of English.

Finally, here are examples which combine temporal and spatial tense: 

4.7)	le nanmu puzu vu batci le gerku
	The man [past] [long time] [long space] bites the dog.
	Long ago and far away, the man bit the dog.

Alternatively, 

4.8)	le nanmu batci le gerku puzuvuku
	The man bites the dog [past] [long time] [long space].
	The man bit the dog long ago and far away.

5. Interval sizes: VEhA and ZEhA

The following cmavo are discussed in this section: 

	ve'i	VEhA	short space interval
	ve'a	VEhA	medium space interval
	ve'u	VEhA	long space interval

	ze'i	ZEhA	short time interval
	ze'a	ZEhA	medium time interval
	ze'u	ZEhA	long time interval
So far, we have considered only events that are usually thought of as happening at a particular point in space and time: a man biting a dog at a specified place and time. But Lojbanic events may be much more ``spread out'' than that: ``mi vasxu'' (I breathe) is something which is true during the whole of my life from birth to death, and over the entire part of the earth where I spend my life. The cmavo of VEhA (for space) and ZEhA (for time) can be added to any of the tense constructs we have already studied to specify the size of the space or length of the time over which the bridi is claimed to be true. 

5.1)	le verba ve'i cadzu le bisli
	The child [small space interval] walks-on the ice.
	In a small space, the child walks on the ice.
	The child walks about a small area of the ice.
means that her walking was done in a small area. Like the distances, the interval sizes are classified only roughly as ``small, medium, large'', and are relative to the context: a small part of a room might be a large part of a table in that room.

Here is an example using a time interval: 

5.2)	le verba ze'a cadzu le bisli
	The child [medium time interval] walks-on the ice.
	For a medium time, the child walks/walked/will walk
		on the ice.
Note that with no time direction word, Example 5.2 does not say when the walking happened: that would be determined by context. It is possible to specify both directions or distances and an interval, in which case the interval always comes afterward: 

5.3)	le verba pu ze'a
		cadzu le bisli
	The child [past] [medium time interval]
		walks-on the ice.
	For a medium time, the child walked on the ice.
	The child walked on the ice for a while.
In Example 5.3, the relationship of the interval to the specified point in time or space is indeterminate. Does the interval start at the point, end at the point, or is it centered on the point? By adding an additional direction cmavo after the interval, this question can be conclusively answered: 

5.4)	mi ca ze'ica cusku dei
	I [present] [short time interval -- present]
		express this-utterance.
	I am now saying this sentence.
means that for an interval starting a short time in the past and extending to a short time in the future, I am expressing the utterance which is Example 5.4. Of course, ``short'' is relative, as always in tenses. Even a long sentence takes up only a short part of a whole day; in a geological context, the era of Homo sapiens would only be a ``ze'i'' interval.

By contrast, 

5.5)	mi ca ze'ipu
		cusku dei
	I [present] [short time interval -- past]
		express this-utterance.
	I have just been saying this sentence.
means that for a short time interval extending from the past to the present I have been expressing Example 5.5. Here the imaginary journey starts at the present, lays down one end point of the interval, moves into the past, and lays down the other endpoint. Another example: 

5.6)	mi pu ze'aba citka le mi sanmi
	I [past] [medium time interval - future] eat my meal.
	For a medium time afterward, I ate my meal.
	I ate my meal for a while.

With ``ca'' instead of ``ba'', Example 5.6 becomes Example 5.7, 

5.7)	mi pu ze'aca citka le mi sanmi
	I [past] [medium time interval - present] eat my meal
	For a medium time before and afterward, I ate my meal.
	I ate my meal for a while.
because the interval would then be centered on the past moment rather than oriented toward the future of that moment. The colloquial English translations are the same --- English is not well-suited to representing this distinction.

Here are some examples of the use of space intervals with and without specified directions: 

5.8)	ta ri'u ve'i finpe
	that-there [right] [short space interval] is-a-fish
	That thing on my right is a fish.

In Example 5.8, there is no equivalent in the colloquial English translation of the ``small interval'' which the fish occupies. Neither the Lojban nor the English expresses the orientation of the fish. Compare Example 5.9: 

5.9)	ta ri'u ve'ica'u
		finpe
	that-there [right] [short space interval - front]
		is-a-fish
	That thing on my right extending forwards is a fish.

Here the space interval occupied by the fish extends from a point on my right to another point in front of the first point.

6. Vague intervals and non-specific tenses

What is the significance of failing to specify an interval size of the type discussed in Section 5? The Lojban rule is that if no interval size is given, the size of the space or time interval is left vague by the speaker. For example: 

6.1)	mi pu klama le zarci
	I [past] go-to the market.
really means:

At a moment in the past, and possibly other moments as well, the event ``I went to the market'' was in progress.
The vague or unspecified interval contains an instant in the speaker's past. However, there is no indication whether or not the whole interval is in the speaker's past! It is entirely possible that the interval during which the going-to-the-market is happening stretches into the speaker's present or even future.

Example 6.1 points up a fundamental difference between Lojban tenses and English tenses. An English past-tense sentence like ``I went to the market'' generally signifies that the going-to-the-market is entirely in the past; that is, that the event is complete at the time of speaking. Lojban ``pu'' has no such implication.

This property of a past tense is sometimes called ``aorist'', in reference to a similar concept in the tense system of Classical Greek. All of the Lojban tenses have the same property, however: 

6.3)	le tricu ba crino
	the tree [future] is-green
	The tree will be green.
does not imply (as the colloquial English translation does) that the tree is not green now. The vague interval throughout which the tree is, in fact, green may have already started.

This general principle does not mean that Lojban has no way of indicating that a tree will be green but is not yet green. Indeed, there are several ways of expressing that concept: see Section 10 (event contours) and Section 20 (logical connection between tenses).

7. Dimensionality: VIhA

The following cmavo are discussed in this section: 

	vi'i	VIhA	on a line
	vi'a	VIhA	in an area
	vi'u	VIhA	through a volume
	vi'e	VIhA	throughout a space/time interval
The cmavo of ZEhA are sufficient to express time intervals. One fundamental difference between space and time, however, is that space is multi-dimensional. Sometimes we want to say not only that something moves over a small interval, but also perhaps that it moves in a line. Lojban allows for this. I can specify that a motion ``in a small space'' is more specifically ``in a short line'', ``in a small area'', or ``through a small volume''.

What about the child walking on the ice in Examples 5.1 through 5.3? Given the nature of ice, probably the area interpretation is most sensible. I can make this assumption explicit with the appropriate member of selma'o VIhA: 

7.1)	le verba ve'a vi'a
		cadzu le bisli
	The child [medium space interval] [2-dimensional]
		walks-on the ice.
	In a medium-sized area, the child walks on the ice.
Space intervals can contain either VEhA or VIhA or both, but if both, VEhA must come first, as Example 7.1 shows.

The reader may wish to raise a philosophical point here. (Readers who don't wish to, should skip this paragraph.) The ice may be two-dimensional, or more accurately its surface may be, but since the child is three-dimensional, her walking must also be. The subjective nature of Lojban tense comes to the rescue here: the action is essentially planar, and the third dimension of height is simply irrelevant to walking. Even walking on a mountain could be called ``vi'a'', because relatively speaking the mountain is associated with an essentially two-dimensional surface. Motion which is not confined to such a surface (e.g., flying, or walking through a three-dimensional network of tunnels, or climbing among mountains rather than on a single mountain) would be properly described with ``vi'u''. So the cognitive, rather than the physical, dimensionality controls the choice of VIhA cmavo.

VIhA has a member ``vi'e'' which indicates a 4-dimensional interval, one that involves both space and time. This allows the spatial tenses to invade, to some degree, the temporal tenses; it is possible to make statements about space-time considered as an Einsteinian whole. (There are presently no cmavo of FAhA assigned to ``pastward'' and ``futureward'' considered as space rather than time directions --- they could be added, though, if Lojbanists find space-time expression useful.) If a temporal tense cmavo is used in the same tense construct with a ``vi'e'' interval, the resulting tense may be self-contradictory.

8. Movement in space: MOhI

The following cmavo is discussed in this section: 

	mo'i	MOhI	movement flag
All the information carried by the tense constructs so far presented has been presumed to be static: the bridi is occurring somewhere or other in space and time, more or less remote from the speaker. Suppose the truth of the bridi itself depends on the result of a movement, or represents an action being done while the speaker is moving? This too can be represented by the tense system, using the cmavo ``mo'i'' (of selma'o MOhI) plus a spatial direction and optional distance; the direction now refers to a direction of motion rather than a static direction from the speaker. 

8.1)	le verba mo'i ri'u cadzu le bisli
	The child [movement] [right] walks-on the ice.
	The child walks toward my right on the ice.

This is quite different from: 

8.2)	le verba ri'u cadzu le bisli
	The child [right] walks-on the ice.
	To the right of me, the child walks on the ice.
In either case, however, the reference frame for defining ``right'' and ``left'' is the speaker's, not the child's. This can be changed thus: 

8.3)	le verba mo'i ri'u cadzu le bisli
		ma'i vo'a
	The child [movement] [right] walks on the ice
		in-reference-frame the-x1-place.
	The child walks toward her right on the ice.
Example 8.3 is analogous to Example 8.1. The cmavo ``ma'i'' belongs to selma'o BAI (explained in Chapter 9), and allows specifying a reference frame.

Both a regular and a ``mo'i''-flagged spatial tense can be combined, with the ``mo'i'' construct coming last: 

8.4)	le verba zu'avu mo'i ri'uvi
		cadzu le bisli
	The child [left] [long] [movement] [right] [short]
		walks-on the ice.
	Far to the left of me, the child walks a short
		distance toward my right on the ice.
It is not grammatical to use multiple directions like ``zu'a ca'u'' after ``mo'i'', but complex movements can be expressed in a separate bridi.

Here is an example of a movement tense on a bridi not inherently involving movement: 

8.5)	mi mo'i ca'uvu citka le mi sanmi
	I [movement] [front] [long] eat my meal.
	While moving a long way forward, I eat my meal.
(Perhaps I am eating in an airplane.)

There is no parallel facility in Lojban at present for expressing movement in time --- time travel --- but one could be added easily if it ever becomes useful.

9. Interval properties: TAhE and ``roi''

The following cmavo are discussed in this section: 

	di'i	TAhE	regularly
	na'o	TAhE	typically
	ru'i	TAhE	continuously
	ta'e	TAhE	habitually

	di'inai	TAhE	irregularly
	na'onai	TAhE	atypically
	ru'inai	TAhE	intermittently
	ta'enai	TAhE	contrary to habit

	roi	ROI	``n'' times
	roinai	ROI	other than ``n'' times

	ze'e	ZEhA	whole time interval
	ve'e	VEhA	whole space interval
Consider Lojban bridi which express events taking place in time. Whether a very short interval (a point) or a long interval of time is involved, the event may not be spread consistently throughout that interval. Lojban can use the cmavo of selma'o TAhE to express the idea of continuous or non-continuous actions. 

9.1)	mi puzu ze'u
		velckule
	I [past] [long distance] [long interval]
		am-a-school-attendee (pupil).
	Long ago I attended school for a long time.
probably does not mean that I attended school continuously throughout the whole of that long-ago interval. Actually, I attended school every day, except for school holidays. More explicitly, 

9.2)	mi puzu ze'u di'i
		velckule
	I [past] [long distance] [long interval] [regularly]
		am-a-pupil.
	Long ago I regularly attended school for a long time.
The four TAhE cmavo are differentiated as follows: ``ru'i'' covers the entirety of the interval, ``di'i'' covers the parts of the interval which are systematically spaced subintervals; ``na'o'' covers part of the interval, but exactly which part is determined by context; ``ta'e'' covers part of the interval, selected with reference to the behavior of the actor (who often, but not always, appears in the x1 place of the bridi).

Using TAhE does not require being so specific. Either the time direction or the time interval or both may be omitted (in which case they are vague). For example: 

9.3)	mi ba ta'e klama le zarci
	I [future] [habitually] go-to the market.
	I will habitually go to the market.
	I will make a habit of going to the market.
specifies the future, but the duration of the interval is indefinite. Similarly, 

9.4)	mi na'o klama le zarci
	I [typically] go-to the market
	I typically go/went/will go to the market
illustrates an interval property in isolation. There are no distance or direction cmavo, so the point of time is vague; likewise, there is no interval cmavo, so the length of the interval during which these goings-to-the-market take place is also vague. As always, context will determine these vague values.

``Intermittently'' is the polar opposite notion to ``continuously'', and is expressed not with its own cmavo, but by adding the negation suffix ``-nai'' (which belongs to selma'o NAI) to ``ru'i''. For example: 

9.5)	le verba ru'inai cadzu le bisli
	The child [continuously-not] walks-on the ice.
	The child intermittently walks on the ice.
As shown in the cmavo table above, all the cmavo of TAhE may be negated with ``-nai''; ``ru'inai'' and ``di'inai'' are probably the most useful.

An intermittent event can also be specified by counting the number of times during the interval that it takes place. The cmavo ``roi'' (which belongs to selma'o ROI) can be appended to a number to make a quantified tense. Quantified tenses are common in English, but not so commonly named: they are exemplified by the adverbs ``never'', ``once'', ``twice'', ``thrice'', ... ``always'', and by the related phrases ``many times'', ``a few times'', ``too many times'', and so on. All of these are handled in Lojban by a number plus ``-roi'': 

9.6)	mi paroi klama le zarci
	I [one time] go-to the market.
	I go to the market once.

9.7)	mi du'eroi klama le zarci
	I [too-many times] go-to the market.
	I go to the market too often.
With the quantified tense alone, we don't know whether the past, the present, or the future is intended, but of course the quantified tense need not stand alone: 

9.8)	mi pu reroi klama le zarci
	I [past] [two times] go-to the market.
	I went to the market twice.
The English is slightly over-specific here: it entails that both goings-to- the-market were in the past, which may or may not be true in the Lojban sentence, since the implied interval is vague. Therefore, the interval may start in the past but extend into the present or even the future.

Adding ``-nai'' to ``roi'' is also permitted, and has the meaning ``other than (the number specified)'': 

9.9)	le ratcu reroinai citka le cirli
	The rat [twice-not] eats the cheese.
	The rat eats the cheese other than twice

This may mean that the rat eats the cheese fewer times, or more times, or not at all.

It is necessary to be careful with sentences like Example 9.6 and Example 9.8, where a quantified tense appears without an interval. What Example 9.8 really says is that during an interval of unspecified size, at least part of which was set in the past, the event of my going to the market happened twice. The example says nothing about what happened outside that vague time interval. This is often less than we mean. If we want to nail down that I went to the market once and only once, we can use the cmavo ``ze'e'' which represents the ``whole time interval'': conceptually, an interval which stretches from time's beginning to its end: 

9.10)	mi ze'e paroi klama le zarci
	I [whole interval] [once] go-to the market.

Since specifying no ZEhA leaves the interval vague, Example 9.8 might in appropriate context mean the same as Example 9.10 after all --- but Example 9.10 allows us to be specific when specificity is necessary.

A PU cmavo following ``ze'e'' has a slightly different meaning from one that follows another ZEhA cmavo. The compound cmavo ``ze'epu'' signifies the interval stretching from the infinite past to the reference point (wherever the imaginary journey has taken you); ``ze'eba'' is the interval stretching from the reference point to the infinite future. The remaining form, ``ze'eca'', makes specific the ``whole of time'' interpretation just given. These compound forms make it possible to assert that something has never happened without asserting that it never will. 

9.11)	mi ze'epu noroi klama le zarci
	I [whole interval] [past] [never] go-to the market.
	I have never gone to the market.
says nothing about whether I might go in future.

The space equivalent of ``ze'e'' is ``ve'e'', and it can be used in the same way with a quantified space tense: see Section 11 for an explanation of space interval modifiers.

10. Event contours: ZAhO and ``re'u''

The following cmavo are discussed in this section: 

	pu'o	ZAhO	inchoative
	ca'o	ZAhO	continuitive
	ba'o	ZAhO	perfective
	co'a	ZAhO	initiative
	co'u	ZAhO	cessitive
	mo'u	ZAhO	completitive
	za'o	ZAhO	superfective
	co'i	ZAhO	achievative
	de'a	ZAhO	pausative
	di'a	ZAhO	resumptive
	re'u	ROI	ordinal tense
The cmavo of selma'o ZAhO express the Lojban version of what is traditionally called ``aspect''. This is not a notion well expressed by English tenses, but many languages (including Chinese and Russian among Lojban's six source languages) consider it more important than the specification of mere position in time.

The ``event contours'' of selma'o ZAhO, with their bizarre keywords, represent the natural portions of an event considered as a process, an occurrence with an internal structure including a beginning, a middle, and an end. Since the keywords are scarcely self-explanatory, each ZAhO will be explained in detail here. Note that from the viewpoint of Lojban syntax, ZAhOs are interval modifiers like TAhEs or ROI compounds; if both are found in a single tense, the TAhE/ROI comes first and the ZAhO afterward. The imaginary journey described by other tense cmavo moves us to the portion of the event-as-process which the ZAhO specifies.

It is important to understand that ZAhO cmavo, unlike the other tense cmavo, specify characteristic portions of the event, and are seen from an essentially timeless perspective. The ``beginning'' of an event is the same whether the event is in the speaker's present, past, or future. It is especially important not to confuse the speaker-relative viewpoint of the PU tenses with the event-relative viewpoint of the ZAhO tenses.

The cmavo ``pu'o'', ``ca'o'', and ``ba'o'' (etymologically derived from the PU cmavo) refer to an event that has not yet begun, that is in progress, or that has ended, respectively: 

10.1)	mi pu'o damba
	I [inchoative] fight.
	I'm on the verge of fighting.

10.2)	la stiv. ca'o bacru
	Steve [continuitive] utters.
	Steve continues to talk.

10.3)	le verba ba'o cadzu le bisli
	The child [perfective] walks-on the ice.
	The child is finished walking on the ice.
As discussed in Section 6, the simple PU cmavo make no assumptions about whether the scope of a past, present, or future event extends into one of the other tenses as well. Examples 10.1 through 10.3 illustrate that these ZAhO cmavo do make such assumptions possible: the event in 10.1 has not yet begun, definitively; likewise, the event in 10.3 is definitely over.

Note that in Example 10.1 and Example 10.3, ``pu'o'' and ``ba'o'' may appear to be reversed: ``pu'o'', although etymologically connected with ``pu'', is referring to a future event; whereas ``ba'o'', connected with ``ba'', is referring to a past event. This is the natural result of the event-centered view of ZAhO cmavo. The inchoative, or ``pu'o'', part of an event, is in the ``pastward'' portion of that event, when seen from the perspective of the event itself. It is only by inference that we suppose that Example 10.1 refers to the speaker's future: in fact, no PU tense is given, so the inchoative part of the event need not be coincident with the speaker's present: ``pu'o'' is not necessarily, though in fact often is, the same as ``ca pu'o''.

The cmavo in Examples 10.1 through 10.3 refer to spans of time. There are also two points of time that can be usefully associated with an event: the beginning, marked by ``co'a'', and the end, marked by ``co'u''. Specifically, ``co'a'' marks the boundary between the ``pu'o'' and ``ca'o'' parts of an event, and ``co'u'' marks the boundary between the ``ca'o'' and ``ba'o'' parts: 

10.4)	mi ba co'a citka le mi sanmi
	I [future] [initiative] eat my meal.
	I will begin to eat my meal.

10.5)	mi pu co'u citka le mi sanmi
	I [past] [cessitive] eat my meal.
	I ceased eating my meal.

Compare Example 10.4 with: 

10.6)	mi ba di'i co'a bajra
	I [future] [regularly] [initiative] run.
	I will regularly begin to run.
which illustrates the combination of a TAhE with a ZAhO.

A process can have two end points, one reflecting the ``natural end'' (when the process is complete) and the other reflecting the ``actual stopping point'' (whether complete or not). Example 10.5 may be contrasted with: 

10.7)	mi pu mo'u citka le mi sanmi
	I [past] [completitive] eat my meal.
	I finished eating my meal.

In Example 10.7, the meal has reached its natural end; in Example 10.5, the meal has merely ceased, without necessarily reaching its natural end.

A process such as eating a meal does not necessarily proceed uninterrupted. If it is interrupted, there are two more relevant point events: the point just before the interruption, marked by ``de'a'', and the point just after the interruption, marked by ``di'a''. Some examples: 

10.8)	mi pu de'a citka le mi sanmi
	I [past] [pausative] eat my meal.
	I stopped eating my meal
		(with the intention of resuming).

10.9)	mi ba di'a citka le mi sanmi
	I [future] [resumptive] eat my meal.
	I will resume eating my meal.
In addition, it is possible for a process to continue beyond its natural end. The span of time between the natural and the actual end points is represented by ``za'o'': 

10.10)	le xirma ca za'o
		jivna bajra
	The horse [present] [superfective]
		compete-type-of runs.
	The horse keeps on running a race too long.
which means that it ran past the finish line (after the race was over --- in most races, the runners do not stop right at the finish line).

An entire event can be treated as a single moment using the cmavo ``co'i'': 

10.11)	la djan. pu co'i catra la djim
	John [past] [achievative] kills Jim.
	John was at the point in time where he killed Jim.
Finally, since an activity is cyclical, an individual cycle can be referred to using a number followed by ``re'u'', which is the other cmavo of selma'o ROI: 

10.12)	mi pare'u klama le zarci
	I [first time] go-to the store.
	I go to the store for the first time
		(within a vague interval).

Note the difference between: 

10.13)	mi pare'u paroi klama le zarci
	I [first time] [one time] go-to the store.
	For the first time, I go to the store once.
and 

10.14)	mi paroi pare'u klama le zarci
	I [one time] [first time] go-to the store.
	There is one occasion on which I go to
		the store for the first time.

11. Space interval modifiers: FEhE

The following cmavo is discussed in this section: 

		fe'e	FEhE	space interval modifier flag
Like time intervals, space intervals can also be continuous, discontinuous, or repetitive. Rather than having a whole separate set of selma'o for space interval properties, we instead prefix the flag ``fe'e'' to the cmavo used for time interval properties. A space interval property would be placed just after the space interval size and/or dimensionality cmavo: 

11.1)	ko vi'i fe'e di'i
		sombo le gurni
	You-imperative [1-dimensional] [space:] [regularly]
		sow the grain.
	Sow the grain in a line and evenly!

11.2)	mi fe'e ciroi
		tervecnu lo selsalta
	I [space:] [three places]
		buy those-which-are salad-ingredients.
	I buy salad ingredients in three locations.

11.3)	ze'e roroi ve'e
		fe'e roroi ku
		li re su'i re du li vo
	[whole time] [all times] [whole space]
		[space:] [all places]
		The-number 2 + 2 = the-number 4.
	Always and everywhere, two plus two is four.

As shown in Example 11.3, when a tense comes first in a bridi, rather than in its normal position before the selbri (in this case ``du''), it is emphasized.

The ``fe'e'' marker can also be used for the same purpose before members of ZAhO. (The cmavo ``be'a'' belongs to selma'o FAhA; it is the space direction meaning ``north of''.) 

11.4)	tu ve'abe'a
		fe'e co'a rokci
	that-yonder [medium space interval - north]
		[space] [initiative] is-a-rock.
	That is the beginning of a rock extending to my north.
	That is the south face of a rock.
Here the notion of a ``beginning point'' represented by the cmavo ``co'a'' is transferred from ``beginning in time'' to ``beginning in space'' under the influence of the ``fe'e'' flag. Space is not inherently oriented, unlike time, which flows from past to future: therefore, some indication of orientation is necessary, and the ``ve'abe'a'' provides an orientation in which the south face is the ``beginning'' and the north face is the ``end'', since the rock extends from south (near me) to north (away from me).

Many natural languages represent time by a space-based metaphor: in English, what is past is said to be ``behind us''. In other languages, the metaphor is reversed. Here, Lojban is representing space (or space interval modifiers) by a time-based metaphor: the choice of a FAhA cmavo following a VEhA cmavo indicates which direction is mapped onto the future. (The choice of future rather than past is arbitrary, but convenient for English-speakers.)

If both a TAhE (or ROI) and a ZAhO are present as space interval modifiers, the ``fe'e'' flag must be prefixed to each.

12. Tenses as sumti tcita

So far, we have seen tenses only just before the selbri, or (equivalently in meaning) floating about the bridi with ``ku''. There is another major use for tenses in Lojban: as sumti tcita, or argument tags. A tense may be used to add spatial or temporal information to a bridi as, in effect, an additional place: 

12.1)	mi klama le zarci ca le nu
		do klama le zdani
	I go-to the market [present] the event-of
		you go-to the house.
	I go to the market when you go to the house.
Here ``ca'' does not appear before the selbri, nor with ``ku''; instead, it governs the following sumti, the ``le nu'' construct. What Example 12.1 asserts is that the action of the main bridi is happening at the same time as the event mentioned by that sumti. So ``ca'', which means ``now'' when used with a selbri, means ``simultaneously-with'' when used with a sumti. Consider another example: 

12.2)	mi klama le zarci pu le nu
		do pu klama le zdani
	I go-to the market [past] the event-of
		you [past] go-to the house.

The second ``pu'' is simply the past tense marker for the event of your going to the house, and says that this event is in the speaker's past. How are we to understand the first ``pu'', the sumti tcita?

All of our imaginary journeys so far have started at the speaker's location in space and time. Now we are specifying an imaginary journey that starts at a different location, namely at the event of your going to the house. Example 12.2 then says that my going to the market is in the past, relative not to the speaker's present moment, but instead relative to the moment when you went to the house. Example 12.2 can therefore be translated:

I had gone to the market before you went to the house.
(Other translations are possible, depending on the ever-present context.) Spatial direction and distance sumti tcita are exactly analogous: 

12.3)	le ratcu cu citka le cirla vi le panka
	The rat eats the cheese [short distance] the park.
	The rat eats the cheese near the park.

12.4)	le ratcu cu citka le cirla
		vi le vu panka
	The rat eats the cheese
		[short distance] the [long distance] park
	The rat eats the cheese near the faraway park.

12.5)	le ratcu cu citka le cirla
		vu le vi panka
	The rat eats the cheese
		[long distance] the [short distance] park
	The rat eats the cheese far away from the nearby park.
The event contours of selma'o ZAhO (and their space equivalents, prefixed with ``fe'e'') are also useful as sumti tcita. The interpretation of ZAhO tcita differs from that of FAhA, VA, PU, and ZI tcita, however. The event described in the sumti is viewed as a process, and the action of the main bridi occurs at the phase of the process which the ZAhO specifies, or at least some part of that phase. The action of the main bridi itself is seen as a point event, so that there is no issue about which phase of the main bridi is intended. For example: 

12.6)	mi morsi ba'o le nu mi jmive
	I am-dead [perfective] the event-of I live.
	I die in the aftermath of my living.

Here the (point-)event of my being dead is the portion of my living-process which occurs after the process is complete. Contrast Example 12.6 with: 

12.7)	mi morsi ba le nu mi jmive
	I am-dead [future] the event-of I live.

As explained in Section 6, Example 12.7 does not exclude the possibility that I died before I ceased to live!

Likewise, we might say: 

12.8)	mi klama le zarci pu'o le nu mi citka
	I go-to the store [inchoative] the event-of I eat
which indicates that before my eating begins, I go to the store, whereas 

12.9)	mi klama le zarci ba'o le nu mi citka
	I go-to the store [perfective] the event-of I eat
would indicate that I go to the store after I am finished eating.

Here is an example which mixes temporal ZAhO (as a tense) and spatial ZAhO (as a sumti tcita): 

12.10)	le bloti pu za'o xelklama
		fe'e ba'o le lalxu
	the boat [past] [superfective]
		is-a-transport-mechanism
		[space] [perfective] the lake.
	The boat sailed for too long and beyond the lake.

Probably it sailed up onto the dock. One point of clarification: although ``xelklama'' appears to mean simply ``is-a-mode-of-transport'', it does not -- the bridi of Example 12.10 has four omitted arguments, and thus has the (physical) journey which goes on too long as part of its meaning.

The remaining tense cmavo, which have to do with interval size, dimension, and continuousness (or lack thereof) are interpreted to let the sumti specify the particular interval over which the main bridi operates: 

12.11)	mi klama le zarci reroi le ca djedi
	I go-to the market [twice] the [present] day
	I go/went/will go to the market twice today.
Be careful not to confuse a tense used as a sumti tcita with a tense used within a seltcita sumti: 

12.12)	loi snime cu carvi
		ze'u le ca dunra
	some-of-the-mass-of snow rains
		[long time interval] the [present] winter.
	Snow falls during this winter.
claims that the interval specified by ``this winter'' is long, as events of snowfall go, whereas 

12.13)	loi snime cu carvi
		ca le ze'u dunra
	some-of-the-mass-of snow rains
		[present] the [long time] winter.
	Snow falls in the long winter.
claims that during some part of the winter, which is long as winters go, snow falls.

13. Sticky and multiple tenses: KI

The following cmavo is discussed in this section: 

	ki	KI	sticky tense set/reset
So far we have only considered tenses in isolated bridi. Lojban provides several ways for a tense to continue in effect over more than a single bridi. This property is known as ``stickiness'': the tense gets ``stuck'' and remains in effect until explicitly ``unstuck''. In the metaphor of the imaginary journey, the place and time set by a sticky tense may be thought of as a campsite or way-station: it provides a permanent origin with respect to which other tenses are understood. Later imaginary journeys start from that point rather than from the speaker.

To make a tense sticky, suffix ``ki'' to it: 

13.1)	mi puki klama le zarci
		.i le nanmu cu batci le gerku
	I [past] [sticky] go-to the market.
		 The man bites the dog.
	I went to the market.  The man bit the dog.

Here the use of ``puki'' rather than just ``pu'' ensures that the tense will affect the next sentence as well. Otherwise, since the second sentence is tenseless, there would be no way of determining its tense; the event of the second sentence might happen before, after, or simultaneously with that of the first sentence.

(The last statement does not apply when the two sentences form part of a narrative. See Section 14 for an explanation of ``story time'', which employs a different set of conventions.)

What if the second sentence has a tense anyway? 

13.2)	mi puki klama le zarci
		.i le nanmu pu batci le gerku
	I [past] sticky go-to the market.
		 The man [past] bites the dog.

Here the second ``pu'' does not replace the sticky tense, but adds to it, in the sense that the starting point of its imaginary journey is taken to be the previously set sticky time. So the translation of Example 13.2 is: 

13.3)	I went to the market.
		The man had earlier bitten the dog.
and it is equivalent in meaning (when considered in isolation from any other sentences) to: 

13.4)	mi pu klama le zarci
		.i le nanmu pupu batci le gerku
	I [past] go-to the market.
		The man [past] [past] bites the dog.
The point has not been discussed so far, but it is perfectly grammatical to have more than one tense construct in a sentence: 

13.5)	puku mi ba klama le zarci
	[past] I [future] go-to the market.
	Earlier, I was going to go to the market.

Here there are two tenses in the same bridi, the first floating free and specified by ``puku'', the second in the usual place and specified by ``ba''. They are considered cumulative in the same way as the two tenses in separate sentences of Example 13.4. Example 13.5 is therefore equivalent in meaning, except for emphasis, to: 

13.6)	mi puba klama le zarci
	I [past] [future] go-to the market.
	I was going to go to the market.
Compare Example 13.7 and Example 13.8, which have a different meaning from Example 13.5 and Example 13.6: 

13.7)	mi ba klama le zarci puku
	I [future] go-to the market [past].
	I will have gone to the market earlier.

13.8)	mi bapu klama le zarci
	I [future] [past] go-to the market.
	I will have gone to the market.

So when multiple tense constructs in a single bridi are involved, order counts --- the tenses cannot be shifted around as freely as if there were only one tense to worry about.

But why bother to allow multiple tense constructs at all? They specify separate portions of the imaginary journey, and can be useful in order to make part of a tense sticky. Consider Example 13.9, which adds a second bridi and a ``ki'' to Example 13.5:

13.9
pukiku mi ba klama le zarci .i le nanmu cu batci le gerku [past] [sticky] I [future] go-to the market. The man bites the dog.

What is the implied tense of the second sentence? Not ``puba'', but only ``pu'', since only ``pu'' was made sticky with ``ki''. So the translation is:

I was going to go to the market. The man bit the dog.
Lojban has several ways of embedding a bridi within another bridi: descriptions, abstractors, relative clauses. (Technically, descriptions contain selbri rather than bridi.) Any of the selbri of these subordinate bridi may have tenses attached. These tenses are interpreted relative to the tense of the main bridi: 

13.10)	mi pu klama le ba'o zarci
	I [past] go-to the [perfective] market
	I went to the former market.

The significance of the ``ba'o'' in Example 13.10 is that the speaker's destination is described as being ``in the aftermath of being a market''; that is, it is a market no longer. In particular, the time at which it was no longer a market is in the speaker's past, because the ``ba'o'' is interpreted relative to the ``pu'' tense of the main bridi.

Here is an example involving an abstraction bridi: 

13.11)	mi ca jinvi le du'u mi ba morsi
	I now opine the fact-that I will-be dead.
	I now believe that I will be dead.

Here the event of being dead is said to be in the future with respect to the opinion, which is in the present.

``ki'' may also be used as a tense by itself. This cancels all stickiness and returns the bridi and all following bridi to the speaker's location in both space and time: 

13.12)	mi ki cusku dei
	I [here and now] express this-utterance.
	I say this sentence now.
In complex descriptions, multiple tenses may be saved and then used by adding a subscript to ``ki''. A time made sticky with ``kixipa'' (ki-sub-1) can be returned to by specifying ``kixipa'' as a tense by itself. In the case of written expression, the writer's here-and-now is often different from the reader's, and a pair of subscripted ``ki'' tenses could be used to distinguish the two.

14. Story time

Making strict use of the conventions explained in Section 13 would be intolerably awkward when a story is being told. The time at which a story is told by the narrator is usually unimportant to the story. What matters is the flow of time within the story itself. The term ``story'' in this section refers to any series of statements related in more-or-less time-sequential order, not just a fictional one.

Lojban speakers use a different set of conventions, commonly called ``story time'', for inferring tense within a story. It is presumed that the event described by each sentence takes place some time more or less after the previous ones. Therefore, tenseless sentences are implicitly tensed as ``what happens next''. In particular, any sticky time setting is advanced by each sentence.

The following mini-story illustrates the important features of story time. A sentence-by-sentence explication follows: 

14.1)	puzuki ku ne'iki le kevna
		le ninmu goi ko'a zutse le rokci
	[past] [long] [sticky] [,] [inside] [sticky] the cave,
		the woman defined-as she-1 sat-on the rock
	Long ago, in a cave, a woman sat on a rock.

14.2)	.i ko'a citka loi kanba rectu
	She-1 [tenseless] eat some-of-the-mass-of goat flesh.
	She was eating goat's meat.

14.3)	.i ko'a pu jukpa ri le mudyfagri
	She [past] cook the-last-mentioned
		by-method the wood-fire.
	She had cooked the meat over a wood fire.

14.4)	.i lei rectu cu zanglare
	The-mass-of flesh is-(favorable)-warm.
	The meat was pleasantly warm.

14.5)	.i le labno goi ko'e bazaki
		nenri klama le kevna
	The wolf defined-as it-2 [future] [medium] [sticky]
		within-came to-the cave.
	A while later, a wolf came into the cave.

14.6)	.i ko'e lebna lei rectu ko'a
	It-2 [tenseless] takes the-mass-of flesh from-her-1.
	It took the meat from her.

14.7)	.i ko'e bartu klama
	It-2 out ran
	It ran out.
Example 14.1 sets both the time (long ago) and the place (in a cave) using ``ki'', just like the sentence sequences in Section 13. No further space cmavo are used in the rest of the story, so the place is assumed to remain unchanged. The English translation of Example 14.1 is marked for past tense also, as the conventions of English storytelling require: consequently, all other English translation sentences are also in the past tense. (We don't notice how strange this is; even stories about the future are written in past tense!) This conventional use of past tense is not used in Lojban narratives.

Example 14.2 is tenseless. Outside story time, it would be assumed that its event happens simultaneously with that of Example 14.1, since a sticky tense is in effect; the rules of story time, however, imply that the event occurs afterwards, and that the story time has advanced (changing the sticky time set in Example 14.1).

Example 14.3 has an explicit tense. This is taken relative to the latest setting of the sticky time; therefore, the event of Example 14.3 happens before that of Example 14.2. It cannot be determined if Example 14.3 happens before or after Example 14.1.

Example 14.4 is again tenseless. Story time was not changed by the flashback in Example 14.3, so Example 14.4 happens after Example 14.2.

Example 14.5 specifies the future (relative to Example 14.4) and makes it sticky. So all further events happen after Example 14.5.

Example 14.6 and Example 14.7 are again tenseless, and so happen after Example 14.5. (Story time is changed.)

So the overall order is 14.1 - 14.3 - 14.2 - 14.4 - (medium interval) - 14.5 - 14.6 - 14.7. It is also possible that 14.3 happens before 14.1.

If no sticky time (or space) is set initially, the story is set at an unspecified time (or space): the effect is like that of choosing an arbitrary reference point and making it sticky. This style is common in stories that are jokes. The same convention may be used if the context specifies the sticky time sufficiently.

15. Tenses in subordinate bridi

English has a set of rules, formally known as ``sequence of tense rules'', for determining what tense should be used in a subordinate clause, depending on the tense used in the main sentence. Here are some examples: 

15.1)	John says that George is going to the market.

15.2)	John says that George went to the market.

15.3)	John said that George went to the market.

15.4)	John said that George had gone to the market.

In Example 15.1 and Example 15.2, the tense of the main sentence is the present: ``says''. If George goes when John speaks, we get the present tense ``is going'' (``goes'' would be unidiomatic); if George goes before John speaks, we get the past tense ``went''. But if the tense of the main sentence is the past, with ``said'', then the tense required in the subordinate clause is different. If George goes when John speaks, we get the past tense ``went''; if George goes before John speaks, we get the past-perfect tense ``had gone''.

The rule of English, therefore, is that both the tense of the main sentence and the tense of the subordinate clause are understood relative to the speaker (not John, but the person who speaks Examples 15.1 through 15.4).

Lojban, like Russian and Esperanto, uses a different convention. A tense in a subordinate bridi is understood to be relative to the tense already set in the main bridi. Thus Examples 15.1 through 15.4 can be expressed in Lojban respectively thus: 

15.5)	la djan. ca cusku le se du'u
		la djordj. ca klama le zarci
	John [present] says the statement-that
		George [present] goes-to the market.

15.6)	la djan. ca cusku le se du'u
		la djordj. pu klama le zarci
	John [present] says the statement-that
		George [past] goes-to the market.

15.7)	la djan. pu cusku le se du'u
		la djordj. ca klama le zarci
	John [past] says the statement-that
		George [present] goes-to the market.

15.8)	la djan. pu cusku le se du'u
		la djordj. pu klama le zarci
	John [past] says the statement-that
		George [past] goes-to the market.

Probably the most counterintuitive of the Lojban examples is Example 15.7. The ``ca'' looks quite odd, as if George were going to the market right now, rather than back when John spoke. But this ``ca'' is really a ``ca'' with respect to a reference point specified by the outer ``pu''. This behavior is the same as the additive behavior of multiple tenses in the same bridi, as explained in Section 13.

There is a special cmavo ``nau'' (of selma'o CUhE) which can be used to override these rules and get to the speaker's current reference point. (Yes, it sounds like English ``now''.) It is not grammatical to combine ``nau'' with any other cmavo in a tense, except by way of a logical or non-logical connection (see Section 20). Here is a convoluted sentence with several nested bridi which uses ``nau'' at the lowest level: 

15.9)	la djan. pu cusku le se du'u
		la .alis pu cusku le se du'u
			la djordj. pu cusku le se du'u
				la maris. nau klama le zarci
	John [past] says the statement-that
		Alice [past] says the statement-that
			George [past] says the statement that
				Mary [now] goes-to the market.
	John said that Alice had said that George had earlier
		said that Mary is now going to the market.
The use of ``nau'' does not affect sticky tenses.

16. Tense relations between sentences

The sumti tcita method, explained in Section 12, of asserting a tense relationship between two events suffers from asymmetry. Specifically, 

16.1)	le verba cu cadzu le bisli
		zu'a le nu le nanmu cu batci le gerku
	The child walks-on the ice
		[left] the event-of the man bites the dog.
	The child walks on the ice to the left of where
		the man bites the dog.
which specifies an imaginary journey leftward from the man biting the dog to the child walking on the ice, claims only that the child walks on the ice. By the nature of ``le nu'', the man's biting the dog is merely referred to without being claimed. If it seems desirable to claim both, each event can be expressed as a main sentence bridi, with a special form of ``.i'' connecting them: 

16.2)	le nanmu cu batci le gerku
		.izu'abo le verba cu cadzu le bisli
	The man bites the dog.
		[Left] the child walks-on the ice.
	The  man bites the dog.  To the left, the child
		walks on the ice.
``.izu'abo'' is a compound cmavo: the ``.i'' separates the sentences and the ``zu'a'' is the tense. The ``bo'' is required to prevent the ``zu'a'' from gobbling up the following sumti, namely ``le verba''.

Note that the bridi in Example 16.2 appear in the reverse order from their appearance in Example 16.1. With ``.izu'abo'' (and all other afterthought tense connectives) the sentence specifying the origin of the journey comes first. This is a natural order for sentences, but requires some care when converting between this form and the sumti tcita form.

Example 16.2 means the same thing as: 

16.3)	le nanmu cu batci le gerku
		.i zu'a la'edi'u
		le verba cu cadzu le bisli
	The man bites the dog.
		[Left] the-referent-of-the-last-sentence
		the child walks-on the ice.
	The man bites the dog.
		Left of what I just mentioned,
		the child walks on the ice.
If the ``bo'' is omitted, the meaning changes: 

16.4)	le nanmu cu batci le gerku
		.i zu'a le verba cu cadzu le bisli
	The man bites the dog.
		 [Left] the child [something] walks-on the ice.
	The man bites the dog. To the left of the child,
		something walks on the ice.

Here the first place of the second sentence is unspecified, because ``zu'a'' has absorbed the sumti ``le verba''.

Do not confuse either Example 16.2 or Example 16.4 with the following: 

16.5)	le nanmu cu batci le gerku
		.i zu'aku le verba cu cadzu le bisli
	The man bites the dog.
		[Left] the child walks-on the ice.
	The man bites the dog.  Left of me, the child walks
		on the ice.

In Example 16.5, the origin point is the speaker, as is usual with ``zu'aku''. Example 16.2 makes the origin point of the tense the event described by the first sentence.

Two sentences may also be connected in forethought by a tense relationship. Just like afterthought tense connection, forethought tense connection claims both sentences, and in addition claims that the time or space relationship specified by the tense holds between the events the two sentences describe.

The origin sentence is placed first, preceded by a tense plus ``gi''. Another ``gi'' is used to separate the sentences: 

16.6)	pugi mi klama le zarci gi mi klama le zdani
	[past] I go-to the market [,] I go-to the house.
	Before I go to the market, I go to the house.

A parallel construction can be used to express a tense relationship between sumti: 

16.7)	mi klama pugi le zarci gi le zdani
	I go-to [past] the market [,] the house.

Because English does not have any direct way of expressing a tense-like relationship between nouns, Example 16.7 cannot be expressed in English without paraphrasing it either into Example 16.6 or else into ``I go to the house before the market'', which is ambiguous --- is the market going?

Finally, a third forethought construction expresses a tense relationship between bridi-tails rather than whole bridi. (The construct known as a ``bridi-tail'' is explained fully in Chapter 14; roughly speaking, it is a selbri with any following sumti.) Example 16.8 is equivalent in meaning to Example 16.6 and Example 16.7: 

16.8)	mi pugi klama le zarci gi klama le zdani
	I [past] go-to the market [,] go-to the house.
	I, before going to the market, go to the house.
In both Example 16.7 and Example 16.8, the underlying sentences ``mi klama le zarci'' and ``mi klama le zdani'' are not claimed; only the relationship in time between them is claimed.

Both the forethought and the afterthought forms are appropriate with PU, ZI, FAhA, VA, and ZAhO tenses. In all cases, the equivalent forms are (where X and Y stand for sentences, and TENSE for a tense cmavo):

subordinate: X TENSE le nu Y afterthought coordinate: Y .i+TENSE+bo X forethought coordinate: TENSE+gi X gi Y

17. Tensed logical connectives

The Lojban tense system interacts with the Lojban logical connective system. That system is a separate topic, explained in Chapter 14 and touched on only in summary here. By the rules of the logical connective system, Example 17.1 through 17.3 are equivalent in meaning: 

17.1)	la teris. satre le mlatu
		.ije la teris. satre le ractu
	Terry strokes the cat.
		And Terry strokes the rabbit.

17.2)	la teris. satre le mlatu gi'e satre le ractu
	Terry strokes the cat and strokes the rabbit.

17.3)	la teris. satre le mlatu .e le ractu
	Terry strokes the cat and the rabbit.
Suppose we wish to add a tense relationship to the logical connective ``and''? To say that Terry strokes the cat and later strokes the rabbit, we can combine a logical connective with a tense connective by placing the logical connective first, then the tense, and then the cmavo ``bo'', thus: 

17.4)	la teris. satre le mlatu
		.ijebabo la teris. satre le ractu
	Terry strokes the cat.
		And then Terry strokes the rabbit.

17.5)	la teris. satre le mlatu gi'ebabo satre le ractu
	Terry strokes the cat, and then strokes the rabbit.

17.6)	la teris. satre le mlatu .ebabo le ractu
	Terry strokes the cat and then the rabbit.
Example 17.4 through 17.6 are equivalent in meaning. They are also analogous to Examples 17.1 through 17.3 respectively. The ``bo'' is required for the same reason as in Example 16.2: to prevent the ``ba'' from functioning as a sumti tcita for the following sumti (or, in Example 17.5, from being attached to the following selbri).

... ke'e"> ... tu'u"> In addition to the ``bo'' construction of Examples 17.4 through 17.6, there is also a form of tensed logical connective with ``ke ... ke'e'' (``tu'e... tu'u'' for sentences). The logical connective system makes Examples 17.7 through 17.9 equivalent in meaning: 

17.7)	mi bevri le dakli
		.ije tu'e mi bevri le gerku
			.ija mi bevri le mlatu tu'u
	I carry the sack.
		And (I carry the dog.
			And/or I carry the cat).
	I carry the sack. And I carry the dog, or I carry
		the cat, or I carry both.

17.8)	mi bevri le dakli
		gi'eke bevri le gerku gi'a bevri le mlatu
	I carry the sack
		and (carry the dog and/or carry the cat).
	I carry the sack, and also carry the dog
		or carry the cat or carry both.

17.9)	mi bevri le dakli .eke le gerku .a le mlatu
	I carry the sack and (the dog or the cat)
	I carry the sack and also the dog or the cat or both.

Note the uniformity of the Lojban, as contrasted with the variety of ways in which the English provides for the correct grouping. In all cases, the meaning is that I carry the sack in any case, and either the cat or the dog or both.

To express that I carry the sack first (earlier in time), and then the dog or the cat or both simultaneously, I can insert tenses to form Examples 17.10 through 17.12: 

17.10)	mi bevri le dakli
		.ije ba tu'e mi bevri le gerku
			.ijacabo mi bevri le mlatu tu'u
	I carry the sack.
		And [future] (I carry the dog.
			And/or [present] I carry the cat.)
	I carry the sack. And then I will carry the dog
		or I will carry the cat or I will carry both
		at once.

17.11)	mi bevri le dakli
		gi'ebake bevri le gerku
			gi'acabo bevri le mlatu
	I carry the sack
		and [future] (carry the dog
			and/or [present] carry the cat).
	I carry the sack and then will carry the dog
		or carry the cat or carry both at once.

17.12)	mi bevri le dakli
		.ebake bevri le gerku .acabo le mlatu
	I carry the sack and
		[future] (the cat and/or [present] the dog).
	I carry the sack, and then the cat or the dog
		or both at once.
Examples 17.10 through 17.12 are equivalent in meaning to each other, and correspond to the tenseless Examples 17.7 through 17.9 respectively.

18. Tense negation

Any bridi which involves tenses of selma'o PU, FAhA, or ZAhO can be contradicted by a ``-nai'' suffixed to the tense cmavo. Some examples: 

18.1)	mi punai klama le zarci
	I [past] [not] go-to the market.
	I didn't go to the market.
As a contradictory negation, Example 18.1 implies that the bridi as a whole is false without saying anything about what is true. When the negated tense is a sumti tcita, ``-nai'' negation indicates that the stated relationship does not hold: 

18.2)	mi klama le zarci canai le nu
		do klama le zdani
	I go-to the market [present] [not] the event-of
		you go-to the house.
	It is not true that I went to the market at the same
		time that you went to the house.

18.3)	le nanmu batci le gerku ne'inai le kumfa
	The man bites the dog [within] [not] the room.
	The man didn't bite the dog inside the room.

18.4)	mi morsi ca'onai le nu mi jmive
	I am-dead [continuitive - negated] the event-of I live.
	It is false that I am dead during my life.
It is also possible to perform scalar negation of whole tense constructs by placing a member of NAhE before them. Unlike contradictory negation, scalar negation asserts a truth: that the bridi is true with some tense other than that specified. The following examples are scalar negation analogues of Examples 18.1 to 18.3: 

18.5)	mi na'e pu klama le zarci
	I [non-] [past] go-to the market.
	I go to the market other than in the past.

18.6)	le nanmu batci le gerku to'e ne'i le kumfa
	The man bites the dog [opposite-of] [within] the room.
	The man bites the dog outside the room.

18.7)	mi klama le zarci na'e ca le nu
		do klama le zdani
	I go-to the market [non-] [present] the event-of
		you go-to the house.
	I went to the market at a time other than the time at
		which you went to the house.

18.8)	mi morsi na'e ca'o le nu mi jmive
	I am-dead [non-] [continuitive] the event-of I live.
	I am dead other than during my life.
Unlike ``-nai'' contradictory negation, scalar negation of tenses is not limited to PU and FAhA: 

18.9)	le verba na'e ri'u cadzu le bisli
	The child [non-] [right] walks-on the ice
	The child walks on the ice other than to my right.
The use of ``-nai'' on cmavo of TAhE and ROI has already been discussed in Section 9; this use is also a scalar negation.

19. Actuality, potentiality, capability: CAhA

The following cmavo are discussed in this section: 

	ca'a	CAhA	actually is
	ka'e	CAhA	is innately capable of
	nu'o	CAhA	can but has not
	pu'i	CAhA	can and has
Lojban bridi without tense markers may not necessarily refer to actual events: they may also refer to capabilities or potential events. For example: 

19.1)	ro datka cu flulimna
	all ducks are-float-swimmers
	All ducks swim by floating.
is a Lojban truth, even though the colloquial English translation is false or at best ambiguous. This is because the tenseless Lojban bridi doesn't necessarily claim that every duck is swimming or floating now or even at a specific time or place. Even if we add a tense marker to Example 19.1, 

19.2)	ro datka ca flulimna
	all ducks [present] are-float-swimmers.
	All ducks are now swimming by floating.
the resulting Example 19.2 might still be considered a truth, even though the colloquial English seems even more likely to be false. All ducks have the potential of swimming even if they are not exercising that potential at present. To get the full flavor of ``All ducks are now swimming'', we must append a marker from selma'o CAhA to the tense, and say: 

19.3)	ro datka ca ca'a flulimna
	all ducks [present] [actual] are-float-swimmers
	All ducks are now actually swimming by floating.
A CAhA cmavo is always placed after any other tense cmavo, whether for time or for space. However, a CAhA cmavo comes before ``ki'', so that a CAhA condition can be made sticky.

Example 19.3 is false in both Lojban and English, since it claims that the swimming is an actual, present fact, true of every duck that exists, whereas in fact there is at least one duck that is not swimming now.

Furthermore, some ducks are dead (and therefore sink); some ducks have just hatched (and do not know how to swim yet), and some ducks have been eaten by predators (and have ceased to exist as separate objects at all). Nevertheless, all these ducks have the innate capability of swimming --- it is part of the nature of duckhood. The cmavo ``ka'e'' expresses this notion of innate capability: 

19.4)	ro datka ka'e flulimna
	all ducks [capable] are-float-swimmers.
	All ducks are innately capable of swimming.
Under some epistemologies, innate capability can be extended in order to apply the innate properties of a mass to which certain individuals belong to the individuals themselves, even if those individuals are themselves not capable of fulfilling the claim of the bridi. For example: 

19.5)	la djan. ka'e viska
	John [capable] sees.
	John is innately capable of seeing.
	John can see.
might be true about a human being named John, even though he has been blind since birth, because the ability to see is innately built into his nature as a human being. It is theoretically possible that conditions might occur that would enable John to see (a great medical discovery). On the other hand, 

19.6)	le cukta ka'e viska
	The book [capable] sees.
	The book can see.
is not true in most epistemologies, since the ability to see is not part of the innate nature of a book.

Consider once again the newly hatched ducks mentioned earlier. They have the potential of swimming, but have not yet demonstrated that potential. This may be expressed using ``nu'o'', the cmavo of CAhA for undemonstrated potential: 

19.7)	ro cifydatka nu'o flulimna
	all infant-ducks [can but has not] are-float-swimmers.
	All infant ducks have an undemonstrated potential
		for swimming by floating.
	Baby ducks can swim but haven't yet.
Contrariwise, if Frank is not blind from birth, then ``pu'i'' is appropriate: 

19.8)	la frank. pu'i viska
	Frank [can and has] sees.
	Frank has demonstrated a potential for seeing.
	Frank can see and has seen.
Note that the glosses given at the beginning of this section for ``ca'a'', ``nu'o'', and ``pu'i'' incorporate ``ca'' into their meaning, and are really correct for ``ca ca'a'', ``ca nu'o'', and ``ca pu'i''. However, the CAhA cmavo are perfectly meaningful with other tenses than the present: 

19.9)	mi pu ca'a klama le zarci
	I [past] [actual] go-to the store.
	I actually went to the store.

19.10)	la frank. pu nu'o klama le zdani
	Frank [past] [can but has not] goes-to the store.
	Frank could have, but will not have, gone to the
		store (at some understood moment in the
		future).
As always in Lojban tenses, a missing CAhA can have an indeterminate meaning, or the context can be enough to disambiguate it. Saying 

19.11)	ta jelca
	That burns/is-burning/might-burn/will-burn.
with no CAhA specified can translate the two very different English sentences ``That is on fire'' and ``That is inflammable.'' The first demands immediate action (usually), whereas the second merely demands caution. The two cases can be disambiguated with: 

19.12)	ta ca ca'a jelca
	That [present] [actual] burns.
	That is on fire.
and 

19.13)	ta ka'e jelca
	That [capable] burns.
	That is capable of burning.
	That is inflammable.
When no indication is given, as in the simple observative 

19.14)	fagri
	fire
the prudent Lojbanist will assume the meaning ``Fire!''

20. Logical and non-logical connections between tenses

Like many things in Lojban, tenses may be logically connected; logical connection is explained in more detail in Chapter 14. Some of the terminology in this section will be clear only if you already understand logical connectives.

The appropriate logical connectives belong to selma'o JA. A logical connective between tenses can always be expanded to one between sentences: 

20.1)	mi pu je ba klama le zarci
	I [past] and [future] go-to the market.
	I went and will go to the market.
means the same as: 

20.2)	mi pu klama le zarci
		.ije mi ba klama le zarci
	I [past] go-to the market.
		And I [future] go-to the market.
	I went to the market, and I will go to the market.
Tense connection and tense negation are combined in: 

20.3)	mi punai je canai je ba
		klama le zarci
	I [past] [not] and [present] [not] and [future]
		go-to the market.
	I haven't yet gone to the market, but I will in future.
Example 20.3 is far more specific than 

20.4)	mi ba klama le zarci
	I [future] go-to the market.
which only says that I will go, without claiming anything about my past or present. ``ba'' does not imply ``punai'' or ``canai''; to compel that interpretation, either a logical connection or a ZAhO is needed.

Tense negation can often be removed in favor of negation in the logical connective itself. The following examples are equivalent in meaning: 

20.5)	mi mo'izu'anai je mo'iri'u cadzu
	I [motion] [left-not] and [motion] [right] walk.
	I walk not leftward but rightward.

20.6)	mi mo'izu'a naje mo'iri'u cadzu
	I [motion] [left] not-and [motion] [right] walk.
	I walk not leftward but rightward.
There are no forethought logical connections between tenses allowed by the grammar, to keep tenses simpler. Nor is there any way to override simple left-grouping of the connectives, the Lojban default.

The non-logical connectives of selma'o JOI, BIhI, and GAhO are also permitted between tenses. One application is to specify intervals not by size, but by their end-points (``bi'o'' belongs to selma'o BIhI, and connects the end-points of an ordered interval, like English ``from ... to''): 

20.7)	mi puza bi'o bazu vasxu
	I [past] [medium] from ... to [future] [long] breathe.
	I breathe from a medium time ago till a long time
		to come.
(It is to be hoped that I have a long life ahead of me.)

One additional use of non-logical connectives within tenses is discussed in Section 21. Other uses will probably be identified in future.

21. Sub-events

Another application of non-logical tense connection is to talk about sub-events of events. Consider a six-shooter: a gun which can fire six bullets in succession before reloading. If I fire off the entire magazine twice, I can express the fact in Lojban thus: 

21.1)	mi reroi pi'u xaroi
		cecla le seldanti
	I [twice] [cross-product] [six times]
		shoot the projectile-launcher.
	On two occasions, I fire the gun six times.
It would be confusing, though grammatical, to run the ``reroi'' and the ``xaroi'' directly together. However, the non-logical connective ``pi'u'' expresses a Cartesian product (also known as a cross product) of two sets. In this case, there is a set of two firings each of which is represented by a set of six shots, for twelve shots in all (hence the name ``product'': the product of 2 and 6 is 12). Its use specifies very precisely what occurs.

In fact, you can specify strings of interval properties and event contours within a single tense without the use of a logical or non-logical connective cmavo. This allows tenses of the type: 

21.2)	la djordj. ca'o co'a ciska
	George [continuitive] [initiative] writes.
	George continues to start to write.

21.3)	mi reroi ca'o xaroi darxi le damri
	I [twice] [continuitive] [six times] hit the drum.
	On two occasions, I continue to beat the drum six times.

22. Conversion of sumti tcita: JAI

The following cmavo are discussed in this section: 

	jai	JAI	tense conversion
	fai	FA	indefinite place
Conversion is the regular Lojban process of moving around the places of a place structure. The cmavo of selma'o SE serve this purpose, exchanging the first place with one of the others: 

22.1)	mi cu klama le zarci
	I go-to the market.

22.2)	le zarci cu se klama mi
	The market is-gone-to by-me.
It is also possible to bring a place that is specified by a sumti tcita (for the purposes of this chapter, a tense sumti tcita) to the front, by using ``jai'' plus the tense as the grammatical equivalent of SE: 

22.3)	le ratcu cu citka le cirla vi le panka
	The rat eats the cheese [short distance] the park.
	The rat eats the cheese in the park.

22.4)	le panka cu jai vi citka le cirla fai le ratcu
	The park is-the-place-of eating the cheese by-the rat.
	The park is where the rat eats the cheese.
In Example 22.4, the construction JAI+tense converts the location sumti into the first place. The previous first place has nowhere to go, since the location sumti is not a numbered place; however, it can be inserted back into the bridi with ``fai'', the indefinite member of selma'o FA.

(The other members of FA are used to mark the first, second, etc. places of a bridi explicitly: 

22.5)	fa mi cu klama fe le zarci
means the same as 

22.6)	fe le zarci cu klama fa mi
as well as the simple 

22.7)	mi cu klama le zarci
in which the place structure is determined by position.)

Like SE conversion, JAI+tense conversion is especially useful in descriptions with LE selma'o: 

22.8)	mi viska le jai vi citka be le cirla
	I saw the place-of eating the cheese.

Here the eater of the cheese is elided, so no ``fai'' appears.

Of course, temporal tenses are also usable with JAI: 

22.9)	mi djuno fi le jai ca morsi
		be fai la djan.
	I know about the [present] is-dead
		of-the-one-called ``John''
	I know the time of John's death.
	I know when John died.

23. Tenses versus modals

Grammatically, every use of tenses seen so far is exactly paralleled by some use of modals as explained in Chapter 9. Modals and tenses alike can be followed by sumti, can appear before the selbri, can be used in pure and mixed connections, can participate in JAI conversions. The parallelism is perfect. However, there is a deep difference in the semantics of tense constructs and modal constructs, grounded in historical differences between the two forms. Originally, modals and tenses were utterly different things in earlier versions of Loglan; only in Lojban have they become grammatically interchangeable. And even now, differences in semantics continue to be maintained.

The core distinction is that whereas the modal bridi 

23.1)	mi nelci do mu'i le nu do nelci mi
	I like you with-motivation the event-of you like me.
	I like you because you like me.
places the ``le nu'' sumti in the x1 place of the gismu ``mukti'' (which underlies the modal ``mu'i''), namely the motivating event, the tensed bridi 

23.2)	mi nelci do ba le nu do nelci mi
	I like you after the event-of you like me.
	I like you after you like me.
places the ``le nu'' sumti in the x2 place of the gismu ``balvi'' (which underlies the tense ``ba''), namely the point of reference for the future tense. Paraphrases of Example 23.1 and Example 23.2, employing the brivla ``mukti'' and ``balvi'' explicitly, would be: 

23.3)	le nu do nelci mi cu mukti le nu mi nelci do
	The event-of you like me motivates the event-of I like you
	Your liking me is the motive for my liking you.
and 

23.4)	le nu mi nelci do cu balvi le nu do nelci mi
	The event-of I like you is after the event of you like me.
	My liking you follows (in time) your liking me.
(Note that the paraphrase is not perfect due to the difference in what is claimed; Example 23.3 and Example 23.4 claim only the causal and temporal relationships between the events, not the existence of the events themselves.)

As a result, the afterthought sentence-connective forms of Example 23.1 and Example 23.2 are, respectively: 

23.5)	mi nelci do .imu'ibo do nelci mi
	I like you.  [That is] Because you like me.

23.6)	do nelci mi .ibabo mi nelci do
	You like me.  Afterward, I like you.

In Example 23.5, the order of the two bridi ``mi nelci do'' and ``do nelci mi'' is the same as in Example 23.1. In Example 23.6, however, the order is reversed: the origin point ``do nelci mi'' physically appears before the future-time event ``mi nelci do''. In both cases, the bridi characterizing the event in the x2 place appears before the bridi characterizing the event in the x1 place of ``mukti'' or ``balvi''.

In forethought connections, however, the asymmetry between modals and tenses is not found. The forethought equivalents of Example 23.5 and Example 23.6 are 

23.7)	mu'igi do nelci mi gi mi nelci do
	Because you like me, I like you.
and 

23.8)	bagi do nelci mi gi mi nelci do
	After you like me, I like you.
respectively.

The following modal sentence schemata (where X and Y represent sentences) all have the same meaning:

X .i BAI bo Y BAI gi Y gi X X BAI le nu Y
whereas the following tensed sentence schemata also have the same meaning:

X .i TENSE bo Y TENSE gi X gi Y Y TENSE le nu X
neglecting the question of what is claimed. In the modal sentence schemata, the modal tag is always followed by Y, the sentence representing the event in the x1 place of the gismu that underlies the BAI. In the tensed sentences, no such simple rule exists.

24. Tense questions: ``cu'e''

The following cmavo is discussed in this section: 

	cu'e	CUhE	tense question
There are two main ways to ask questions about tense. The main English tense question words are ``When?'' and ``Where?''. These may be paraphrased respectively as ``At what time?'' and ``At what place?'' In these forms, their Lojban equivalents simply involve a tense plus ``ma'', the Lojban sumti question: 

24.1)	do klama le zdani ca ma
	you go-to the house [present] [what sumti?].
	You go to the house at what time?
	When do you go to the house?

24.2)	le verba vi ma pu
		cadzu le bisli
	The child [short space] [what sumti?] [past]
		walks-on the ice.
	The child at/near what place walked on the ice?
	Where did the child walk on the ice?
There is also a non-specific tense and modal question, ``cu'e'', belonging to selma'o CUhE. This can be used wherever a tense or modal construct can be used. 

24.3)	le nanmu cu'e batci le gerku
	The man [what tense?] bites the dog.
	When/Where/How does the man bite the dog?
Possible answers to Example 24.3 might be: 

24.4)	va
	[medium space].
	Some ways from here.

24.5)	puzu
	[past] [long time].
	A long time ago.

24.6)	vi le lunra
	[short space] The moon.
	On the moon.

24.7)	pu'o
	[inchoative]
	He hasn't yet done so.
or even the modal reply (from selma'o BAI; see Chapter 9): 

24.8)	bai la djan.
	Under John's compulsion.
The only way to combine ``cu'e'' with other tense cmavo is through logical connection, which makes a question that pre-specifies some information: 

24.9)	do puzi je cu'e sombo le gurni
	You [past] [short] and [when?] sow the grain?
	You sowed the grain a little while ago;
		when else do you sow it?

Additionally, the logical connective itself can be replaced by a question word: 

24.10)	la .artr. pu je'i ba nolraitru
	Arthur [past] [which?] [future] is-a-king
	Was Arthur a king or will he be?

Answers to Example 24.10 would be logical connectives such as ``je'', meaning ``both'', ``naje'' meaning ``the latter'', or ``jenai'' meaning ``the former''.

25. Explicit magnitudes

It is a limitation of the VA and ZI system of specifying magnitudes that they can only prescribe vague magnitudes: small, medium, or large. In order to express both an origin point and an exact distance, the Lojban construction called a ``termset'' is employed. (Termsets are explained further in Chapter 14 and Chapter 16.) It is grammatical for a termset to be placed after a tense or modal tag rather than a sumti, which allows both the origin of the imaginary journey and its distance to be specified. Here is an example: 

25.1)	la frank. sanli zu'a nu'i la djordj.
		lu'a lo mitre
			be li mu [nu'u]
	Frank stands [left] [start termset] George
		[quantity] a thing-measuring-in-meters
			the-number 5 [end termset].
	Frank is standing five meters to the left of George.

Here the termset extends from the ``nu'i'' to the implicit ``nu'u'' at the end of the sentence, and includes the terms ``la djordj.'', which is the unmarked origin point, and the tagged sumti ``lo mitre be li mu'', which the cmavo ``la'u'' (of selma'o BAI, and meaning ``with quantity''; see Chapter 9) marks as a quantity. Both terms are governed by the tag ``zu'a''

It is not necessary to have both an origin point and an explicit magnitude: a termset may have only a single term in it. A less precise version of Example 25.1 is: 

25.2)	la frank. sanli zu'a nu'i lu'a
		lo mitre be li mu
	Frank stands [left] [termset] [quantity]
		a thing-measuring-in-meters the-number 5.
	Frank stands five meters to the left.

26. Finally (an exercise for the much-tried reader)

26.1)	a'o do pu seju ba roroi ca'o fe'e su'oroi jimpe
		fi le lojbo temci selsku ciste

27. Summary of tense selma'o

PU
temporal direction pu = past, ca = present, ba = future ZI temporal distance zi = short, za = medium, zu = long ZEhA temporal interval ze'i = short, ze'a = medium, ze'u = long, ze'e = infinite ROI objective quantified tense flag noroi = never, paroi = once, ..., roroi = always, etc. TAhE subjective quantified tense di'i = regularly, na'o = typically, ru'i = continuously, ta'e = habitually ZAhO event contours see Section 10

FAhA
spatial direction see Section 27 VA spatial distance vi = short, va = medium, vu = long VEhA spatial interval ve'i = short, ve'a = medium, ve'u = long, ve'e = infinite VIhA spatial dimensionality vi'i = line, vi'a = plane, vi'u = space, vi'e = space-time FEhE spatial interval modifier flag fe'enoroi = nowhere, fe'eroroi = everywhere, fe'eba'o = beyond, etc. MOhI spatial movement flag mo'i = motion; see Section 27

KI
set or reset sticky tense tense+``ki'' = set, ``ki'' alone = reset CUhE tense question, reference point cu'e = asks for a tense or aspect nau = use speaker's reference point JAI tense conversion jaica = the time of, jaivi = the place of, etc.

27. List of spatial directions and direction-like relations

The following list of FAhA cmavo gives rough English glosses for the cmavo, first when used without ``mo'i'' to express a direction, and then when used with ``mo'i'' to express movement in the direction. When possible, the gismu from which the cmavo is derived is also listed. 

cmavo	gismu	without mo'i		with mo'i
-----	-----	------------		---------
ca'u	crane	in front (of)		forward
ti'a	trixe	behind			backward
zu'a	zunle	on the left (of)	leftward
ri'u	pritu	on the right (of)	rightward
ga'u	gapru	above			upward(ly)
ni'a	cnita	below			downward(ly)
ne'i	nenri	within			into
ru'u	sruri	surrounding		orbiting
pa'o	pagre	transfixing		passing through
ne'a		next to			moving while next to		
te'e		bordering		moving along the border (of)
re'o		adjacent (to)		along
fa'a	farna	towards			arriving at
to'o		away from               departing from
zo'i		inward (from)		approaching
ze'o		outward (from)		receding from
zo'a		tangential (to)		passing (by)
bu'u		coincident (with)	moving to coincide with
be'a	berti	north (of)		northward(ly)
ne'u	snanu	south (of)		southward(ly)
du'a	stuna	east (of)		eastward(ly)
vu'a		west (of)		westward(ly)
Special note on ``fa'a'', ``to'o'', ``zo'i'', and ``ze'o'':

``zo'i'' and ``ze'o'' refer to direction towards or away from the speaker's location, or whatever the origin is.

``fa'a'' and ``to'o'' refer to direction towards or away from some other point.