いい

いい means "good" or "fine". It is an い-adjective, and in front of a noun or in front of です it behaves like any other.

Every other form starts with よ

Its other form is よい, and the negative, the past and every other form are built on that.

The mistake is to build these on いい.

• × いくない → よくない
• × いかった → よかった
• × いくなかった → よくなかった

かっこいい (cool, good-looking) ends in the same いい and changes the same way: かっこよくない, かっこよかった.

Usage notes

These go beyond the four basic forms.

Other forms built on よ

• て-form: よくて

  このみせ店はりょうり料理がよくて、やすいです安いです。

  This restaurant has good food and is cheap.

• Adverb: よく – "well", and also "often"

  よくわかりました。

  I understood well.
  よくえいが映画をみます見ます。

  I often watch movies.

• Conditional: よければ

  よければ、いっしょに一緒にいきません行きませんか。

  If you like, shall we go together?

Set replies

• いいですね – "that's nice", "sounds good", when you like what you have just heard.
• いいですよ – "sure", "go ahead", when you agree to a request.
• いいです by itself, in answer to an offer, usually turns it down: "I'm fine". It can be heard as a yes, so people add a shake of the head or say けっこうです instead.
• もういいです – "that's enough".

Asking permission

After a て-form and も, いいですか asks for permission.

いい and よい

よい can stand in for いい in front of a noun or at the end of a sentence. It belongs to writing and formal speech; in conversation いい is the normal form. In kanji both are written 良い.