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: 高い (tall/expensive), 大きい (big), おいしい (delicious), 新しい (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 (famous) is a な-adjective
- 嫌い (dislike) is a な-adjective
When written in kanji, these words show that the い is part of the kanji itself (綺麗), 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 高い:
Polite Form
| Affirmative | Negative | |
|---|---|---|
| Present | 高いです | 高くないです |
| Past | 高かったです | 高くなかったです |
Plain Form
| Affirmative | Negative | |
|---|---|---|
| Present | 高い | 高くない |
| Past | 高かった | 高くなかった |
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:
| Affirmative | Negative | |
|---|---|---|
| Present | いい | よくない |
| Past | よかった | よくなかった |
You say いい in the present affirmative, but every other form uses よ. 天気がよかった (the weather was good), not いかった.
Modifying Nouns
い-adjectives go directly before the noun with no particle needed:
- 高い山 (a tall mountain)
- おいしい料理 (delicious food)
- 新しい車 (a new car)
Compare this to な-adjectives, which need な before the noun: きれいな花.
Common い-Adjectives
| Japanese | Reading | Meaning |
|---|---|---|
| 大きい | ookii | big |
| 小さい | chiisai | small |
| 高い | takai | tall, expensive |
| 安い | yasui | cheap |
| 新しい | atarashii | new |
| 古い | furui | old (things) |
| 暑い | atsui | hot (weather) |
| 寒い | samui | cold (weather) |
| おいしい | oishii | delicious |
| 楽しい | tanoshii | fun |
| 難しい | muzukashii | difficult |
| 易しい | yasashii | easy, kind |
Example Sentences
この映画は面白い。
This movie is interesting.
昨日は寒かった。
Yesterday was cold.
日本語は難しくない。
Japanese is not difficult.
あの店のラーメンはおいしかった。
That shop's ramen was delicious.
新しいスマホが欲しい。
I want a new smartphone.
今日は天気がよかった。
The weather was good today.