## 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:

*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:

**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.