Negation is explained in detail in Chapter 15. There are two forms of negation in Lojban: contradictory and scalar negation. Contradictory negation expresses what is false, whereas scalar negation says that some alternative to what has been stated is true. A simple example is the difference between “John didn't go to Paris” (contradictory negation) and “John went to (somewhere) other than Paris” (scalar negation).

Contradictory negation involving BAI cmavo is performed by appending -nai (of selma'o NAI) to the BAI. A common use of modals with -nai is to deny a causal relationship:

Example 9.86 denies that the relationship between my liking you (which is asserted) and your liking me (which is not asserted) is one of motivation. Nothing is said about whether you like me or not, merely that that hypothetical liking is not the motivation for my liking you.

Scalar negation is achieved by prefixing na'e (of selma'o NAhE), or any of the other cmavo of NAhE, to the BAI cmavo.

Example 9.87 says that the relationship between the plant's growth and your watering it is not one of motivation: the plant is not motivated to grow, as plants are not something which can have motivation as a rule. Implicitly, some other relationship between watering and growth exists, but Example 9.87 doesn't say what it is (presumably ri'a).

Note: Modals made with fi'o plus a selbri cannot be negated directly. The selbri can itself be negated either with contradictory or with scalar negation, however.