Japanese has two types of adjectives, and they conjugate differently. Mix them up and your sentence breaks. Master the difference and you unlock natural, descriptive Japanese.
i-Adjectives (い形容詞)
Always end in い. They conjugate by themselves - no helper words needed.
| Form | 高い (takai, expensive) | Rule |
|---|---|---|
| Present | 高い | Dictionary form |
| Negative | 高くない | い → くない |
| Past | 高かった | い → かった |
| Past negative | 高くなかった | い → くなかった |
| Adverb | 高く | い → く |
Common i-adjectives: 大きい (big) · 小さい (small) · 新しい (new) · 古い (old) · 美味しい (delicious) · 難しい (difficult) · 楽しい (fun) · 暑い (hot) · 寒い (cold)
na-Adjectives (な形容詞)
Behave more like nouns. They need な when modifying a noun, and use です/だ for conjugation.
| Form | 静か (shizuka, quiet) | Rule |
|---|---|---|
| Present | 静かだ / 静かです | + だ/です |
| Negative | 静かじゃない | + じゃない |
| Past | 静かだった | + だった |
| Past negative | 静かじゃなかった | + じゃなかった |
| Modifying noun | 静かな部屋 | + な + noun |
Common na-adjectives: 静か (quiet) · 綺麗 (beautiful) · 有名 (famous) · 元気 (energetic) · 好き (like) · 嫌い (dislike) · 便利 (convenient) · 大変 (tough) · 簡単 (easy)
The Trap: Adjectives That Look Like i-Adjectives But Aren’t
Some na-adjectives end in い. These are the ones that trip everyone up:
- 綺麗 (kirei, beautiful) - na-adjective! 綺麗な人 (not 綺麗い)
- 嫌い (kirai, dislike) - na-adjective!
- 有名 (yuumei, famous) - na-adjective!
The only way to know? Memorize them. Kanjijo’s flashcards mark each adjective with its type, so you never have to guess.
Using Adjectives to Modify Nouns
i-adjective: 高い本 (takai hon) = expensive book - just place before noun
na-adjective: 静かな部屋 (shizuka na heya) = quiet room - add な before noun
How to Actually Memorize Adjectives
- Learn in pairs: 大きい/小さい, 高い/安い, 新しい/古い - opposites stick together
- SRS flashcards with example sentences beat raw word lists every time
- Mnemonic stories for tricky na-adjectives (綺麗 = ki-rei = “key ray” of beautiful light)
- Writing practice reinforces the kanji behind each adjective
Kanjijo tags every adjective by type and drills them with SRS. Free on iOS.