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:
These structures are illustrated in the following; as you can see, Lojban can
express quite subtle logical distinctions succinctly.
Lojban also supports non-logical connectives,
such as mixed connection and set membership (ordered/un-ordered):
(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.)