So far our examples have been isolated mekso (it is legal to have a bare mekso as a sentence in Lojban) and equation bridi involving du. What about inequalities such as “x < 5”? The answer is to use a bridi with an appropriate selbri, thus:
Here is a partial list of selbri useful in mathematical bridi:
du | x1 is identical to x2, x3, x4, ... |
dunli | x1 is equal/congruent to x2 in/on property/quality/dimension/quantity x3 |
mleca | x1 is less than x2 |
zmadu | x1 is greater than x2 |
dubjavme'a | x1 is less than or equal to x2 [du ja mleca, equal or less] |
dubjavmau | x1 is greater than or equal to x2 [du ja zmadu, equal or greater] |
tamdu'i | x1 is similar to x2 [tarmi dunli, shape-equal] |
turdu'i | x1 is isomorphic to x2 [stura dunli, structure-equal] |
cmima | x1 is a member of set x2 |
gripau | x1 is a subset of set x2 [girzu pagbu, set-part] |
na'ujbi | x1 is approximately equal to x2 [namcu jibni, number-near] |
terci'e | x1 is a component with function x2 of system x3 |
Note the difference between dunli and du; dunli has a third place that specifies the kind of equality that is meant. du refers to actual identity, and can have any number of places:
Lojban bridi can have only one predicate, so the du is not repeated.
Any of these selbri may usefully be prefixed with na, the contradictory negation cmavo, to indicate that the relation is false:
As usual in Lojban, negated bridi say what is false, and do not say anything about what might be true.