14.6. sumti connection

Geks and ijeks are sufficient to state every possible logical connection between two bridi. However, it is often the case that two bridi to be logically connected have one or more portions in common:

Example 14.25. 

la djan. klama le zarci .ije la .alis. klama le zarci

John goes to the market, and Alice goes to the market.

Here only a single sumti differs between the two bridi. Lojban does not require that both bridi be expressed in full. Instead, a single bridi can be given which contains both of the different sumti and uses a logical connective from a different selma'o to combine the two sumti:

Example 14.26. 

la djan .e la .alis. klama le zarci
That-named John and that-named Alice go-to the market.

Example 14.26 means exactly the same thing as Example 14.25: one may be rigorously transformed into the other without any change of logical meaning. This rule is true in general for every different kind of logical connection in Lojban; all of them, with one exception (see Section 14.12), can always be transformed into a logical connection between sentences that expresses the same truth function.

The afterthought logical connectives between sumti are eks, which contain a connective cmavo of selma'o A. If ijeks were used in Example 14.26, the meaning would be changed:

Example 14.27. 

la djan.   .ije
That-named John [is/does-something]. And
la .alis. klama le zarci
that-named Alices goes-to the market.

leaving the reader uncertain why John is mentioned at all.

Any ek may be used between sumti, even if there is no direct English equivalent:

Example 14.28. 

la djan. .o la .alis. klama le zarci
That-named John if-and-only-if that-named Alice goes-to the market.

John goes to the market if, and only if, Alice does.

The second line of Example 14.27 is highly stilted English, but the first line (of which it is a literal translation) is excellent Lojban.

What about forethought sumti connection? As is the case for bridi connection, geks are appropriate. They are not the only selma'o of forethought logical-connectives, but are the most commonly used ones.

Example 14.29. 

ga la djan. gi la .alis. klama le zarci

Either John or Alice (or both) goes to the market.

Of course, eks include all the same patterns of compound cmavo that ijeks do. When na or se is part of an ek, a special writing convention is invoked, as in the following example:

Example 14.30. 

la djan. na.a la .alis. klama le zarci
That-named John only-if that-named Alice goes-to the market.

John goes to the market only if Alice does.

Note the period in na.a. The cmavo of A begin with vowels, and therefore must always be preceded by a pause. It is conventional to write all connective compounds as single words (with no spaces), but this pause must still be marked in writing as in speech; otherwise, the na and a would tend to run together.