So in genki 1, it said that いい is changed to よ when being negative and it becomes よくない, and not いいじゃない. But I was watching a show and someone said いいじゃないですか. So now I'm kind of confused, can someone explain this to me?

Thank you

1 Answer 1


いい is a colloquial form of the adjective よい and is used only in dictionary/prenoun forms. Adjectives are negated not by じゃない, but by conjugation: よい→よくない, 青い→青くない.

じゃない in いいじゃない means isn't it.

To clarify:

  • Xはよい=Xはいい:X is good
  • Xはよくない:X isn't good
  • Xはいいじゃない:X is good, isn't it? (よいじゃない as a combination should be less common, because よい is less colloquial and じゃない is colloquial)
  • Basically, the negative of いい is よくない, never いいじゃない. Treat いいじゃない as its own separate fixed expression.
    – dvx2718
    Feb 9 at 0:59
  • 5
    It is worth mentioning that sometimes 「よくない?」 with a rising intonation can also mean, "Isn't (it) good?". Also with the addition of ん you can sort of negate adjectives with じゃない; however it's quite rare and a bit different in it's meaning. For example: 「いいんじゃない」with a lowered intonation could take on a meaning like, "It's not that (it's) good." Most of the time with a rising intonation it would mean the same as 「いいじゃない」= "Isn't (it) good:?"
    – levikara
    Feb 9 at 1:59
  • "is used only in dictionary/prenoun forms" Isn't いいですね correct?
    – jarmanso7
    Feb 10 at 23:09
  • @jarmanso7 いいですね is correct. いい is in prenoun form. Cf 体言、副詞、形容詞、一部の助動詞の連体形、助詞「の」に付く
    – sundowner
    Feb 11 at 12:22
  • @sundowner, okay, I guess "prenoun form" in Japanese does not really mean (only) "before nouns" strictly speaking, then. This is what I thought because you said "only in dictionary/prenoun forms".
    – jarmanso7
    Feb 12 at 2:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .