## 18.7. Other useful selbri for mekso bridi

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:

Example 18.38.

 li xy. mleca li mu The-number x is-less-than the-number 5.

Here is a partial list of selbri useful in mathematical bridi:

 x1 is identical to x2, x3, x4, ... x1 is equal/congruent to x2 in/on property/quality/dimension/quantity x3 x1 is less than x2 x1 is greater than x2 x1 is less than or equal to x2 [ du ja mleca , equal or less] x1 is greater than or equal to x2 [ du ja zmadu , equal or greater] x1 is similar to x2 [ tarmi dunli , shape-equal] turdu'i x1 is isomorphic to x2 [ stura dunli , structure-equal] x1 is a member of set x2 gripau x1 is a subset of set x2 [ girzu pagbu , set-part] 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:

Example 18.39.

 py. du xy.boi zy. “p” is-identical-to “x” “z” p = x = z

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:

Example 18.40.

 li re su'i re na du li mu the-number 2 + 2 is-not equal-to the-number 5. 2 + 2 ≠ 5

As usual in Lojban, negated bridi say what is false, and do not say anything about what might be true.