Grammar JLPT Level N5 - Lesson 2

Structure of 良(い)い:

Non-Past Form: いい
Non-Past Negative Form: よくない
Past Form: よかった
Past Negative Form: よくなかった

Details about 良(い)い:

The adjective いい translates to 'good' in English. It can be tricky for learners initially because it follows a unique conjugation pattern, unlike other い-Adjectives.

それはいい考(かんが)えだ。
That's a good idea.
この味(あじ)は良(よ)くない。
This flavor isn't good.
その旅行(りょこう)はよかった。
That trip was good.
テストの結果(けっか)はよくなかった。
The test results were not good.

As demonstrated in the examples above, the initial い of いい switches to よ for most conjugations. This irregularity is specific to いい and does not occur with any other adjective.

You may also encounter いい written with its kanji, 良(よ)い. When the kanji is used, it is typically read as よい rather than いい. While the core meaning is the same, よい carries a more formal or slightly dated nuance.

それはいい本(ほん)だ。
That is a good book.
このデザインも良(よ)い。
This design is also quite fine. ('Quite fine' conveys a similar nuance to よい)

Caution

It is important not to mix up the adverb よく with the conjugated form of いい. As an adverb, よく can be written with different kanji and means 'often', 'frequently', or 'well'.

良(い)い