じゃない

じゃない is a colloquial way to express negation in Japanese. It is mostly used in informal spoken Japanese and is equivalent to the English phrase 'is not' or 'are not'.

When negating a noun, simply attach じゃない to the noun. For example, 学生 (がくせい, student) becomes 学生じゃない (がくせいじゃない, is not a student).

For na-adjectives, drop the な and add じゃない. For instance, 静かだ (しずかだ, is quiet) becomes 静かじゃない (しずかじゃない, is not quiet).

It is a casual form, so it's best to use it among friends or in informal situations rather than in formal writing or speech.