Japanese Adjectives: I-Adjectives and Na-Adjectives Explained
Adjectives are where Japanese starts to feel different from European languages. They don’t just sit before a noun: they change form for past and negative, much like verbs do. The good news is that there are only two main types, and once you know which type an adjective belongs to, the rules are very regular.
Two types: i-adjectives and na-adjectives
Japanese adjectives come in two groups, named after how they connect to a noun.
- I-adjectives end in い and go straight before a noun: 高い山 (takai yama, “a tall mountain”), 新しい本 (atarashii hon, “a new book”).
- Na-adjectives take な before a noun: 静かな部屋 (shizuka na heya, “a quiet room”), 有名な店 (yūmei na mise, “a famous shop”).
A few common na-adjectives also end in い, which catches learners out. The ones to remember early are きれい (kirei, “pretty, clean”), きらい (kirai, “disliked”) and ゆうめい (yūmei, “famous”). For きれい (綺麗) and ゆうめい (有名), the kanji give a clue: the final sound is part of the kanji’s reading, not a separate い ending. きらい (嫌い) simply has to be memorised.
Conjugating i-adjectives
To change an i-adjective, drop the final い and add a new ending. In polite speech, add です after the plain form.
| Form | Rule | Example: 高い (expensive, tall) |
|---|---|---|
| Present | no change | 高い（です） takai (desu) |
| Negative | い → くない | 高くない（です） takakunai (desu) |
| Past | い → かった | 高かった（です） takakatta (desu) |
| Past negative | い → くなかった | 高くなかった（です） takakunakatta (desu) |
| Te-form (joining) | い → くて | 高くて takakute |
A common mistake is to say 高いでした for “it was expensive”. The past tense is carried by the adjective itself, so the correct form is 高かったです. You will also hear 高くありません as a more formal polite negative; both are correct.
The one irregular adjective is いい (ii, “good”). It conjugates from its older form よい: よくない, よかった, よくて. The same applies to words built on it, such as かっこいい (“cool”), which becomes かっこよかった.
Conjugating na-adjectives
Na-adjectives behave like nouns. The adjective itself doesn’t change; the copula after it does.
| Form | Polite | Plain |
|---|---|---|
| Present | 静かです | 静かだ |
| Negative | 静かじゃないです / 静かではありません | 静かじゃない |
| Past | 静かでした | 静かだった |
| Past negative | 静かじゃなかったです / 静かではありませんでした | 静かじゃなかった |
| Te-form (joining) | 静かで | |
Joining adjectives together
To say two things about something, use the te-form of the first adjective. English uses “and”, but Japanese doesn’t use と here.
- この店は安くておいしいです。 (“This place is cheap and tasty.”)
- 駅は便利できれいです。 (“The station is convenient and clean.”)
Turning adjectives into adverbs
To describe how something is done, i-adjectives change い to く, and na-adjectives use に:
- 早く起きました。 (“I got up early.”)
- 静かに話してください。 (“Please speak quietly.”)
The same forms combine with なる (“to become”): 寒くなりました (“it’s got cold”), 上手になりたいです (“I want to get good at it”). You will use this pattern constantly when talking about progress, weather and plans.
Adjectives learners use every day
| Japanese | Say it | Meaning and type |
|---|---|---|
| おいしい | oishii | tasty (i) |
| むずかしい | muzukashii | difficult (i) |
| たのしい | tanoshii | fun, enjoyable (i) |
| いそがしい | isogashii | busy (i) |
| べんり | benri | convenient (na) |
| げんき | genki | well, energetic (na) |
| すき | suki | liked (na): 寿司が好きです, “I like sushi” |
| じょうず | jōzu | good at (na): 日本語が上手ですね |
Notice that 好き and 上手 take が, not を, for the thing you like or are good at. Our guide to Japanese particles explains why.
How to practise
When you learn a new adjective, learn its type at the same time, and say all four forms out loud a few times: present, negative, past and past negative. Then use it about your own life: what was your weekend like, what is your city like, what isn’t easy about Japanese? In lessons, a tutor will push you to describe things in your own words, which is where adjective forms stop being a table and become automatic.