What Is Lojban?: `.i la lojban. mo`
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Logical Connectives

Lojban expresses logical connectives so as to unambiguously indicate logical scope (the extent of the expressions being connected), as well as to isolate various non-logical features from the logical ones (as noted above for discursives). Logical connectives may be expressed in forethought forms, in which the relationship is specified before the two terms (both ... and ...); or afterthought forms, in which the relationship is specified between the two terms (..., and ...). The form of logical connectives directly indicates their scope and the associated truth table for the two connected terms. For example, a bare vowel joins sumti (.a 'alternation', a and/or b, a OR b; .e 'conjunction', a AND b). na and nai may be used to negate connected terms (na.a 'conditional', not a OR b, if a then b; .anai 'conditional', a or not b, a if b).

The parallel structures are shown in the following abbreviated table:

	`sumti`	`sumti` forethought	sentences
--
OR (a and/or b)	`.a`	`ga sumti gi sumti`	`.i ja`
AND (a and b)	`.e`	`ge sumti gi sumti`	`.i je`
XOR (a or b, not both)	`.onai`	`go sumti ginai sumti`	`.i jonai`
⇒ (if a then b; a only if b)	`na.a`	`ganai sumti gi sumti`	`.i naja`
⇐ (a if b; if b then a)	`.anai`	`ga sumti ginai sumti`	`.i janai`
--

	`tanru`	`tanru` forethought	compound `bridi`
OR (a and/or b)	`ja`	`gu'a selbri gi selbri`	`gi'a`
AND (a and b)	`je`	`gu'e selbri gi selbri`	`gi'e`
XOR (a or b, not both)	`jonai`	`gu'o selbri ginai selbri`	`gi'onai`
⇒ (if a then b; a only if b)	`naja`	`gu'anai selbri gi selbri`	`nagi'a`
⇐ (a if b)	`janai`	`gu'a selbri ginai selbri`	`gi'anai`

These structures are illustrated in the following; as you can see, Lojban can express quite subtle logical distinctions succinctly.

`mi [cu] citka`	`ti`	`.a`	`ta`	`[vau]`
		`++`
I eat this and/or that.

`mi [cu] citka`	`ti`	`.e`	`ta`	`[vau]`
		`++`
I eat this and that.

`mi [cu] citka`	`ti`	`na.a`	`ta`	`[vau]`
		`++++`
I eat this only if that.

`mi [cu] citka`	`ti`	`.anai`	`ta`	`[vau]`
		`++++`
I eat this if that.

`mi [cu] citka lo`	`titnanba`	`jonai`	`cidjrspageti`	`[vau]`
		`+++++`
I eat the cake-XOR-spaghetti. (I eat something that was either cake or spaghetti — though not both.)

`mi [cu]`	`gu'anai`	`te zarci`	`gi`	`vecnu`	`le toldi [vau]`
	`++++`		`++`
I am if–shopkeeper-of–then–seller-of the butterflies. (If I own a butterfly shop, then I sell butterflies.)

`ganai`	`mi`	`gi`	`do`	`[cu] klama`	`[vau]`
+++++		`++`
If me, then you, go.

`mi [cu] klama [vau]`	`.i je`	`do [cu] klama [vau]`
	`+++`
I go and* you go.*

`mi`	`[cu]`
--

`klama tu [vau]`	`gi'e`	`citka ti [vau]`	`[vau]`
	`+++`
I go to that-yonder and* eat this/these.*

Lojban also supports non-logical connectives, such as mixed connection and set membership (ordered/un-ordered):

`mi`	`[cu]`	`citka`
--

`le`	`blari'o`	`joi`	`pelxu`	`[ku]`	`[vau]`
		`+++`
I eat the blue-green-mixed-with-yellow (stuff).

`mi`	`[cu]`	`citka`
--

`le blari'o ku`	`joi`	`le pelxu [ku]`	`[vau]`
	`+++`
I eat the blue-green (stuff) mixed-with the yellow (stuff).

(The ku before the joi in the latter example cannot be left out due to the ambiguity resolution rules invoked in the definition of Lojban.)

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Attachments to `sumti`, `selbri` and sentences	Up	Brief glossary of Lojban words used in these examples