い-Adjectives | How They Work

What are い-Adjectives?

Japanese has two types of adjectives: い-adjectives and な-adjectives. い-adjectives always end in い and conjugate on their own without any help from です or だ. This makes them different from な-adjectives, which behave more like nouns. Our lesson on Japanese adjectives walks through both types with guided practice, and the adjective conjugation guide covers every form in detail.

Most adjectives you learn early on are い-adjectives: 高(たか)い (tall/expensive), 大(おお)きい (big), おいしい (delicious), 新(あたら)しい (new).

How to Spot an い-Adjective

If a word ends in い and the い is a standalone hiragana character (not part of a kanji), it's usually an い-adjective. The key exceptions are a few な-adjectives that happen to end in い:

• きれい (beautiful) is a な-adjective
• 有名(ゆうめい) (famous) is a な-adjective
• 嫌(きら)い (dislike) is a な-adjective

When written in kanji, these words show that the い is part of the kanji itself (綺麗(きれい)), not a separate conjugatable ending.

Conjugation at a Glance

い-adjectives conjugate by dropping the final い and adding a suffix. Here's the full picture using 高(たか)い:

Polite Form

Plain Form

Each of these forms has its own page with more detail: present, negative, past, past negative.

The いい Exception

The adjective いい (good) is irregular. It was originally よい, and all conjugated forms still use the よ stem:

You say いい in the present affirmative, but every other form uses よ. 天気(てんき)がよかった (the weather was good), not いかった.

Modifying Nouns

い-adjectives go directly before the noun with no particle needed:

• 高(たか)い山(やま) (a tall mountain)
• おいしい料理(りょうり) (delicious food)
• 新(あたら)しい車(くるま) (a new car)

Compare this to な-adjectives, which need な before the noun: きれいな花(はな).

Common い-Adjectives