い-Adjective

An い-adjective is a describing word that ends in い: たかい高い (expensive), おおきい大きい (big), あたらしい新しい (new). It goes straight in front of the noun it describes, with nothing in between, or ends the sentence with です after it for politeness.

The い is the part that changes

To make the negative or the past, drop the final い and add the ending. です after it keeps the sentence polite and never changes itself.

いい (good) is irregular: its forms are よくない, よかった and よくなかった. Words that end in いい, such as かっこいい, change the same way.

Common mistakes

The endings that belong to nouns do not go on an い-adjective. The adjective itself changes, and です stays as it is.

• × 高いではありません → 高くないです
• × 高いでした → 高かったです
• × 高いだ → 高い

A few words end in the sound い but are な-adjectives: きれい (pretty, clean), きらい嫌い (disliked), ゆうめい有名 (famous). They take な in front of a noun and never くない.

• × きれい花, × きれくない → きれいな花, きれいじゃないです

Usage notes

These go beyond the four polite forms.

Without です

In casual speech an い-adjective ends the sentence with nothing after it. It does not take だ: ×暑いだ.

Joining two adjectives

To say "and" after an い-adjective, change い to くて.