The negative form of
る-Verbs are conjugated based on the same set of rules used for other forms of
る-Verb conjugation (removal of る, followed by the addition of something else). In the case of negation, the additional component will be
ない (casual), or
ません (polite).
While the common translation of
ない and
ません is simply ‘not’, they actually have several possible nuances. These nuances are ‘don’t’ (usually not), ‘won’t’ (intentionally not), or ‘can’t’ (unintentionally not).
-
私（わたし）は人（ひと）の名前（なまえ）を覚（おぼ）えない。
I can’t remember people's names. (Unintentionally not)
-
私（わたし）はプレゼントを開（あ）けません。
I won't open the present. (Intentionally not)
Both
ない and
ません are auxiliary verbs (
ません is a conjugation of ます), meaning that they have their own set of conjugation rules.
The ない attached to make the negative form of adjectives is a different word, and therefore follows different conjugation rules. When attached to adjectives ない itself is an い-Adjective, and not an auxiliary verb.