The negative form of い-Adjectives
in Japanese is created by using the 連用形（れんようけい） form of the adjective, followed by ない
. 連用形（れんようけい） form just means ‘agglutinative’, or ‘conjunctive’ in Japanese. For い-Adjectives
, this conjunctive form is created by removing い, and replacing it with く.
used with い-Adjectives
is considered to be a different word to the ない
used with verbs. When used with い-Adjectives
itself is also an い-Adjective
. This means that it follows the same rules as regular い-Adjectives
. Due to ません (the polite negative form) being an auxiliary verb, it cannot be conjugated with い-Adjectives
in the same way as verbs.
This tea don't lukewarm. (Incorrect example, with incorrect English to match!)
This tea is not lukewarm. (Natural Japanese)
As can be seen here, you must first add the verb ある
, and then conjugate it into it’s negative form using the auxiliary verb ません. This is how the polite negative is created.
As with regular い-Adjectives, you cannot use だ after ない. です is acceptable to create a semi-polite form, but is best used in spoken language only.