～くない

The suffix ～くない is used to negate i-adjectives (い形容詞) in Japanese. When you want to express that something does not possess the quality described by the adjective, you simply change the い at the end of the adjective to くない. This allows you to construct negative sentences effortlessly.

For example, if you want to say that something is 'not big', you start with the adjective 大きい (おおきい), remove the い, and add くない to form 大きくない (おおきくない).

It is crucial to remember that ～くない is specifically used with い-adjectives only. If you are dealing with な-adjectives, the negative form would be different (using じゃない). Therefore, ensure you identify the type of adjective before applying this negation.