Key takeaways
- Japanese adjectives come in two grammatically distinct types: i-adjectives (ending in い) and na-adjectives. They conjugate differently for tense, negation, and the adverb form.
- I-adjectives conjugate by changing the い ending: 高い (takai, expensive) – past 高かった (takakatta), negative 高くない (takaku nai), adverb 高く (takaku).
- Na-adjectives use the copula だ/です in predicates and require な when modifying a noun directly: きれいな人 (kirei na hito, a beautiful person) but この人はきれいです (this person is beautiful).
- The adjective いい (ii, good) is irregular: its conjugated forms use よ as the stem (よくない, よかった), not いく or いかった.
Japanese learners from European language backgrounds often expect adjectives to work like they do in Spanish or French: unchanging words that agree with the noun in gender and number.
Japanese adjectives work differently in every direction, they conjugate for tense and negation just like verbs, and the two types (i-adjective and na-adjective) follow completely separate patterns. Getting both systems right is essential for forming any descriptive sentence in Japanese.
This guide covers the complete Japanese adjective system: the two types, how each conjugates, placement in sentences, how adjectives form comparisons and the adverb, and the tricky special cases that catch learners repeatedly.
Adjective errors in Japanese are visible in almost every sentence, a wrong ending or a missing な flags incomplete grammar. italki has connected 10M+ learners with Japanese teachers since 2007, giving learners access to teachers who catch those errors in real conversation before they become fixed habits.
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The two adjective types at a glance
| Type | Dictionary form ends in | Example | Before noun | In predicate |
|---|---|---|---|---|
| i-adjective | い (i) | 高い (takai, expensive) | 高い本 (takai hon) | 本は高い |
| na-adjective | na (added when modifying noun) | きれい (kirei, beautiful) | きれいな人 (kirei na hito) | 人はきれいです |
The きれい trap: きれい ends in い but is a na-adjective, not an i-adjective. Other na-adjectives ending in い: 嫌い (kirai, disliked), 有名 (yuumei, famous). These must use na-adjective conjugation patterns, not i-adjective patterns.
I-adjectives: conjugation table
| Form | Pattern | 高い (takai) | 大きい (ookii) |
|---|---|---|---|
| Non-past positive | -い | 高い | 大きい |
| Non-past negative | -くない | 高くない | 大きくない |
| Past positive | -かった | 高かった | 大きかった |
| Past negative | -くなかった | 高くなかった | 大きくなかった |
| Te-form (connecting) | -くて | 高くて | 大きくて |
| Adverb form | -く | 高く | 大きく |
Polite forms: Add です after the plain form for polite speech: 高いです, 高くないです, 高かったです, 高くなかったです.
| Useful i-adjectives | Meaning |
|---|---|
| 大きい (ookii) | big |
| 小さい (chiisai) | small |
| 新しい (atarashii) | new |
| 古い (furui) | old |
| 長い (nagai) | long |
| 短い (mijikai) | short |
| 難しい (muzukashii) | difficult |
| 易しい (yasashii) | easy |
| 楽しい (tanoshii) | fun, enjoyable |
| 嬉しい (ureshii) | happy, glad |
| 暑い (atsui) | hot (weather/temperature) |
| 寒い (samui) | cold (weather/temperature) |
| 辛い (karai) | spicy; also read つらい (tsurai, painful) |
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Na-adjectives: conjugation table
Na-adjectives use the copula (だ plain, です polite) in predicates. The adjective form itself does not change.
| Form | Pattern | きれい (kirei) | 静か (shizuka) |
|---|---|---|---|
| Non-past positive | adj + だ/です | きれいだ / きれいです | 静かだ / 静かです |
| Non-past negative | adj + ではない / じゃない | きれいじゃない | 静かじゃない |
| Past positive | adj + だった / でした | きれいだった | 静かだった |
| Past negative | adj + ではなかった / じゃなかった | きれいじゃなかった | 静かじゃなかった |
| Before noun | adj + な | きれいな人 | 静かな場所 |
| Te-form (connecting) | adj + で | きれいで | 静かで |
| Adverb form | adj + に | きれいに | 静かに |
| Useful na-adjectives | Meaning |
|---|---|
| 静か (shizuka) | quiet |
| 賑やか (nigiyaka) | lively, bustling |
| 便利 (benri) | convenient |
| 不便 (fuben) | inconvenient |
| 元気 (genki) | healthy, energetic |
| 暇 (hima) | free, not busy |
| 上手 (jouzu) | skilled, good at |
| 下手 (heta) | poor at, unskilled |
| 好き (suki) | liked, favourite |
| 嫌い (kirai) | disliked |
| 大切 (taisetsu) | important, precious |
| 有名 (yuumei) | famous |
A private Japanese tutor can drill both adjective types in the same conversation, describing a restaurant as おいしい (oishii, delicious, i-adjective) and にぎやか (nigiyaka, lively, na-adjective) together, which builds the pattern-switching instinct that only comes from production, not from studying the tables separately. italki has 30,000+ teachers across 150+ languages, including qualified Japanese teachers who integrate grammar into real descriptive tasks from the first session.
Adjectives before nouns vs. in predicates
Both adjective types can appear before a noun (attributive position) or after a noun in a predicate (predicative position). The form changes for na-adjectives.
I-adjectives use the same form in both positions:
- Attributive: 高い山 (takai yama, a tall mountain)
- Predicative: この山は高い (kono yama wa takai, this mountain is tall)
Na-adjectives require な in attributive position but drop it in predicates:
- Attributive: 静かな町 (shizuka na machi, a quiet town)
- Predicative: この町は静かです (kono machi wa shizuka desu, this town is quiet)
Common mistake: Using na-adjective forms without な before a noun: 静か町 is incorrect. Na is not optional in attributive position.
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Comparisons with Japanese adjectives
Japanese uses より (yori, than) and の方が (no hou ga, -er / more) for comparisons, and 一番 (ichiban, most) for superlatives.
Comparative (A is more X than B): AはBより [adjective] 東京は大阪より大きいです。 (Tokyo is bigger than Osaka.) このホテルはあのホテルより静かです。 (This hotel is quieter than that hotel.)
Asking which is more X: AとBとどちらの方が [adjective]？ 東京と大阪とどちらの方が大きいですか？ (Which is bigger, Tokyo or Osaka?)
Superlative (most X): [Group] の中で一番 [adjective] クラスの中で一番難しい試験。 (The hardest exam in the class.) 日本で一番有名な山。 (The most famous mountain in Japan.)
Adverb form
Adjectives form adverbs directly:
- I-adjective: replace い with く: 速い (hayai, fast) – 速く (hayaku, quickly)
- Na-adjective: add に: 静か (shizuka, quiet) – 静かに (shizuka ni, quietly)
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Tricky special cases
いい (ii, good): The most common i-adjective in Japanese is irregular. All conjugated forms use よ as the stem, not い.
| Form | Correct | Wrong |
|---|---|---|
| Non-past | いい / よい | |
| Negative | よくない | いくない |
| Past | よかった | いかった |
| Past negative | よくなかった | いくなかった |
| Adverb | よく | いく |
ない (nai, not exist / none): Acts as an i-adjective.
- Past: なかった
- Te-form: なくて
- Used in verb negatives: 食べない – 食べなかった (past)
きれい, 嫌い, 有名 end in い but are na-adjectives. Always check when an い-ending word seems unusual, if it is Sino-Japanese or a borrowing, it is almost certainly na-adjective class.
Common mistakes
| Error | Correct form | Note |
|---|---|---|
| きれいいです | きれいです | No double い |
| 静かのところ | 静かなところ | Na-adjective needs な before noun |
| 大きかくない | 大きくない | i-adj negative: drop い, add くない |
| いい – いかった | よかった | いい is irregular; conjugate from よ |
| 静かだな人 | 静かな人 | No だ before な in attributive position |
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Using adjectives in real Japanese
The goal is switching between i-adjective and na-adjective patterns automatically in conversation, without stopping to recall which type a word belongs to. That fluency builds through production, using both types in the same sentence, in real descriptions.
Book a trial lesson and describe your home, your neighbourhood, or a recent experience using both adjective types. A teacher who corrects the ending in real time, よかった, not いかった, builds the reflex faster than any written exercise.
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FAQ
What is the difference between i-adjectives and na-adjectives?
I-adjectives conjugate by changing their い ending directly. Na-adjectives do not change form; they use the copula だ/です in predicates and require な when placed before a noun. The easiest check: can you replace the adjective ending with かった to make it past tense? If yes, i-adjective. If not, na-adjective.
Why is きれい a na-adjective if it ends in い?
Japanese adjective type is grammatical, not purely phonetic. Kirei is a Sino-Japanese word (綺麗), and the vast majority of Sino-Japanese words that end in い belong to the na-adjective class. Other examples: 嫌い (kirai), 有名 (yuumei). When in doubt, check a dictionary entry, it will mark adjectives as 形容詞 (i-adjective) or 形容動詞 (na-adjective).
Can I use とても with both types of adjective?
Yes. とても (very) modifies both: とても高い (very expensive, i-adjective) and とても静か (very quiet, na-adjective). The adjective form after totemo follows its standard predicate form.
What does よく mean?
よく is the adverb form of いい/よい (good). It means well, often, or frequently depending on context: よく勉強します (I study often), よくできました (well done), よくわかりません (I do not understand well). It is one of the most common Japanese adverbs.
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