い-Adjectives くない

This grammar is used to negate i-adjectives in plain, polite, or polite formal contexts. Take the い ending of an i-adjective, drop the い, and add くない for plain negation, or くないです / くありません for polite negation. It describes that something does not have the stated quality (not expensive, not big, not interesting, etc.). It is common in everyday conversation and basic writing. Remember to keep the adjective stem unchanged before adding くない.