Japanese Adjective Conjugation: The Complete Guide

You’ve learned that 大きい (おおきい) means “big” and きれい means “pretty.” You can drop them into simple sentences. But then someone asks you how to say “it wasn’t pretty” or “it became cold” — and suddenly your brain goes blank.

Japanese adjectives don’t just sit still. They conjugate — they change their endings to express tense, negation, and more. The good news: once you learn the patterns for each type, every adjective in the language follows the same rules. This guide walks you through every conjugation you need for daily conversation, with examples, common mistakes, and a quick quiz at the end.

At a Glance: い-Adjectives vs な-Adjectives

Feature	い-Adjectives	な-Adjectives
How to recognize them	End in the hiragana い	Do not end in い (usually); need な before a noun
Before a noun	No change: 大きい犬	Add な: きれいな犬
Negative present	drop い → add くない	Add じゃない / ではない
Past affirmative	drop い → add かった	Add だった / でした
Past negative	drop い → add くなかった	Add じゃなかった
て-form	drop い → add くて	Add で
Adverb form	drop い → add く	Add に
Examples	大きい、寒い、高い	きれい、便利、静か
Tricky exception	いい → よ- (not い-) in all conjugations	Some end in い but are な-adj (e.g., きれい)

Part 1: い-Adjectives — Forms and Conjugation

い-adjectives (also called i-adjectives or keiyoushi / 形容詞（けいようし）) always end in the hiragana い in their plain, dictionary form. To conjugate them, you drop the final い and add a new ending.

Here are 10 common い-adjectives to practice with:

Adjective	Reading	Meaning
大きい	おおきい	big
小さい	ちいさい	small
高い	たかい	tall / expensive
安い	やすい	cheap
寒い	さむい	cold (weather)
暑い	あつい	hot (weather)
難しい	むずかしい	difficult
楽しい	たのしい	fun / enjoyable
新しい	あたらしい	new
古い	ふるい	old (objects)

Complete い-Adjective Conjugation Table

Using 寒い (さむい, cold) as the base example:

Form	Rule	Result	Meaning
Dictionary (plain)	—	寒い	is cold
Polite present	drop い → add いです	寒いです	is cold (polite)
Negative (plain)	drop い → add くない	寒くない	is not cold
Negative (polite)	drop い → add くないです / くありません	寒くないです	is not cold (polite)
Past (plain)	drop い → add かった	寒かった	was cold
Past (polite)	drop い → add かったです	寒かったです	was cold (polite)
Past negative (plain)	drop い → add くなかった	寒くなかった	was not cold
Past negative (polite)	drop い → add くなかったです	寒くなかったです	was not cold (polite)
て-form	drop い → add くて	寒くて	cold and… / being cold…
Adverb	drop い → add く	寒く	coldly / in a cold way

The Irregular: いい (good)

The adjective いい (good) is the most important exception in the entire system. When you conjugate it, the stem changes from い- to よ-:

Form	Correct	Wrong (common mistake)
Plain present	いい	—
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~~
て-form	よくて	~~いくて~~

The formal/written counterpart of いい is 良い（よい）, which conjugates normally from the よ- stem. Both mean “good,” but いい is used in speech and よい in formal writing.

Part 2: な-Adjectives — Forms and Conjugation

な-adjectives (also called na-adjectives or keiyoudoushi / 形容動詞（けいようどうし）) behave more like nouns grammatically. They do not change their own ending — instead, you add endings to them, much like you would with a noun followed by だ (is).

Here are 10 common な-adjectives to practice with:

Adjective	Reading	Meaning
きれい	きれい	pretty / clean
静か	しずか	quiet
便利	べんり	convenient
元気	げんき	energetic / well
有名	ゆうめい	famous
大変	たいへん	tough / difficult
暇	ひま	free (time) / bored
上手	じょうず	skilled / good at
丁寧	ていねい	polite / careful
複雑	ふくざつ	complicated

Important note on identification: Some な-adjectives end in the hiragana い, which can cause confusion. きれい (pretty), きらい (dislike), and 嫌い（きらい）are all な-adjectives despite ending in い. There is no shortcut rule — you need to learn these as vocabulary. When in doubt, check a dictionary.

Complete な-Adjective Conjugation Table

Using 静か（しずか, quiet）as the base example:

Form	Rule	Result	Meaning
Dictionary (plain)	adj + だ	静かだ	is quiet
Polite present	adj + です	静かです	is quiet (polite)
Negative (plain)	adj + じゃない / ではない	静かじゃない	is not quiet
Negative (polite)	adj + じゃないです / ではありません	静かじゃないです	is not quiet (polite)
Past (plain)	adj + だった	静かだった	was quiet
Past (polite)	adj + でした	静かでした	was quiet (polite)
Past negative (plain)	adj + じゃなかった	静かじゃなかった	was not quiet
Past negative (polite)	adj + じゃなかったです	静かじゃなかったです	was not quiet (polite)
て-form	adj + で	静かで	quiet and… / being quiet…
Adverb	adj + に	静かに	quietly
Before noun	adj + な + noun	静かな部屋	a quiet room

Part 3: Using Adjectives Before Nouns

When an adjective directly modifies a noun (placed before it), the two types behave differently.

い-Adjectives Before Nouns: No Change

い-adjectives go directly before a noun without any change to their form:

• 大きい犬（おおきいいぬ）— a big dog
• 新しい本（あたらしいほん）— a new book
• 難しい問題（むずかしいもんだい）— a difficult problem

な-Adjectives Before Nouns: Add な

な-adjectives must have な inserted between the adjective and the noun:

• きれいな花（きれいなはな）— a pretty flower
• 有名な俳優（ゆうめいなはいゆう）— a famous actor
• 便利な場所（べんりなばしょ）— a convenient place

Forgetting the な is one of the most common errors English speakers make. If you say ×きれい花, it sounds ungrammatical — the な is not optional. Think of it as a connector: な-adjective + な + noun.

Part 4: Adjective + なる — Expressing Change

To say something “became” or “has become” a certain way, Japanese uses the adjective’s adverb form + なる (to become). The pattern differs slightly between the two adjective types:

• い-adjective: drop い → add く → + なる
• な-adjective: adjective + に + なる

Japanese	Reading	Meaning
寒くなった	さむくなった	It became cold / It got cold
高くなった	たかくなった	It became expensive
難しくなる	むずかしくなる	It will become difficult
よくなった	よくなった	It got better (note: いい → よく)
きれいになった	きれいになった	It became pretty / She became beautiful
静かになる	しずかになる	It will become quiet
元気になった	げんきになった	She got better / He became energetic
有名になった	ゆうめいになった	She became famous

Example sentences in context:

• 最近、日本語が上手くなってきました。(さいきん、にほんごがじょうずくなってきました。) — My Japanese has been getting better lately.
• 春になったら、暖かくなります。(はるになったら、あたたかくなります。) — When spring comes, it will get warm.
• この町は有名になりましたね。(このまちはゆうめいになりましたね。) — This town has become famous, hasn’t it.

Part 5: Stacking Adjectives with the て-Form

When you want to describe something with two or more adjectives (“cold and quiet,” “cheap and convenient”), you connect them using the て-form of each adjective, much like the て-form connects verbs.

Connecting Two い-Adjectives

Use the て-form (drop い → add くて) on all adjectives except the final one:

• 安くておいしい — cheap and delicious
• 広くて明るい部屋（ひろくてあかるいへや）— a spacious and bright room

Connecting Two な-Adjectives

Use the て-form (add で) on all adjectives except the final one:

• 静かで便利な場所 — a quiet and convenient place
• きれいで有名な観光地（かんこうち）— a beautiful and famous tourist spot

Mixing い-Adjectives and な-Adjectives

You can freely mix both types. Convert each adjective to its て-form in sequence, regardless of type:

• 寒くて静かな夜（さむくてしずかなよる）— a cold and quiet night
• 安くてきれいなホテル — a cheap and clean hotel
• 広くて静かで便利なアパート — a spacious, quiet, and convenient apartment

Convention note: Japanese does not have a strict rule about adjective ordering (unlike English, which puts size before color, etc.). However, stacking more than three or four adjectives sounds unnatural. If you have many descriptors, break them into separate sentences.

Part 6: Comparatives and Superlatives

Unlike English (fast → faster → fastest), Japanese adjectives do not change their form for comparison. Instead, comparison is expressed through words placed around the adjective.

Comparative: A is more [adjective] than B

Pattern: A は B より [adjective]

• 東京は大阪より大きいです。(とうきょうはおおさかよりおおきいです。) — Tokyo is bigger than Osaka.
• この部屋はあの部屋より静かです。(このへやはあのへやよりしずかです。) — This room is quieter than that room.

More Comparative: even more [adjective]

Pattern: もっと [adjective]

• もっと安いものはありますか。(もっとやすいものはありますか。) — Is there something cheaper?
• もっと静かに話してください。(もっとしずかにはなしてください。) — Please speak more quietly.

Superlative: the most [adjective]

Pattern: [group] の中で（なかで）一番（いちばん）[adjective]

• クラスの中で一番難しい科目は何ですか。(クラスのなかでいちばんむずかしいかもくはなんですか。) — What is the most difficult subject in the class?
• この店で一番有名な料理はラーメンです。(このみせでいちばんゆうめいなりょうりはラーメンです。) — The most famous dish in this restaurant is ramen.

Notice that the adjective itself (難しい, 有名な) stays completely unchanged. Only the surrounding words carry the comparative meaning.

Part 7: Common Mistakes to Avoid

Mistake 1: Treating な-Adjectives Like い-Adjectives

Because words like きれい, 嫌い（きらい）, and きらい end in い, many learners apply い-adjective conjugation rules to them. This is incorrect:

Mistake	Correct	Notes
✗ きれいくない	✓ きれいじゃない	きれい is a な-adj
✗ きれいかった	✓ きれいだった	な-adj past uses だった
✗ 嫌いくない	✓ 嫌いじゃない	嫌い is also a な-adj

Mistake 2: Forgetting な Before a Noun

This is the single most common error with な-adjectives. The な is mandatory as a connector:

Mistake	Correct
✗ きれい花	✓ きれいな花
✗ 静か部屋	✓ 静かな部屋
✗ 便利駅	✓ 便利な駅

Mistake 3: Using いく/いくない Instead of よく/よくない for いい

The irregular adjective いい (good) is conjugated from the stem よ-, not い-. Applying the standard い-adjective rule produces ungrammatical forms:

• ✗ いかった → ✓ よかった (was good)
• ✗ いくない → ✓ よくない (not good)
• ✗ いくて → ✓ よくて (good and…)

Mistake 4: Using くない Instead of じゃない in て-Form Chains

When negating an adjective in a て-form chain, the negative must also use its て-form. Using the plain negative form breaks the chain:

• ✗ 広くないて明るい → ✓ 広くなくて明るい (not spacious but bright)
• Pattern: negative + て-form of negative = drop い from くない → くなくて

Mistake 5: Adding です Directly to an い-Adjective Negative

Both ×寒いじゃないです and ×寒いではありません are wrong. The polite negative of い-adjectives uses くないです or くありません:

• ✗ 寒いじゃないです
• ✓ 寒くないです / 寒くありません

Decision Flowchart: Is This Adjective い-Type or な-Type?

START: You have an adjective.
          |
          v
Does it end in the hiragana い?
          |
    Yes   |   No
    |         |
    v         v
Does a dictionary list it    --> It is a な-adjective.
as a な-adjective?           --> Use な before nouns.
(e.g., きれい、嫌い、幸い)  --> Conjugate with じゃない / だった / で / に
    |
    | No
    v
It is an い-adjective.
Use it directly before nouns.
Conjugate by dropping い:
  → Negative: くない
  → Past: かった
  → て-form: くて
  → Adverb: く
          |
          v
Is the adjective いい (good)?
          |
    Yes   |   No
    |         |
    v         v
Use よ- stem in all     --> Follow the standard
conjugated forms:            い-adjective rules.
よかった、よくない、よくて

Quick Quiz: Test Yourself

Fill in the blanks with the correct adjective form. Answers are below.

1. 昨日の映画は___（面白い — past affirmative, polite）。 — Yesterday’s movie was interesting.
2. この店は___（きれい — before noun）場所にあります。 — This shop is in a pretty place.
3. 最近、日本語が___（上手 — adjective + なる, past）。— My Japanese has gotten better recently.
4. その映画は___（有名 — negative, polite）と思います。— I don’t think that movie is famous.
5. 部屋は___（広い — て-form）、___（静か — て-form ending）です。— The room is spacious and quiet.
6. このスマホは___（いい — negative, plain）。— This smartphone is not good.

Answers

1. 面白かったです（おもしろかったです）
2. きれいな
3. 上手になりました（じょうずになりました）
4. 有名じゃないです（ゆうめいじゃないです）/ 有名ではないと思います
5. 広くて（ひろくて）、静か（しずか）
6. よくない

Summary: The Conjugation Rules at a Glance

Form	い-Adjective (寒い)	な-Adjective (静か)
Present plain	寒い	静かだ
Present polite	寒いです	静かです
Negative plain	寒くない	静かじゃない
Negative polite	寒くないです	静かじゃないです
Past plain	寒かった	静かだった
Past polite	寒かったです	静かでした
Past neg. plain	寒くなかった	静かじゃなかった
Past neg. polite	寒くなかったです	静かじゃなかったです
て-form	寒くて	静かで
Adverb	寒く	静かに
Before noun	寒い + noun	静かな + noun
+ なる (become)	寒くなる	静かになる

Which adjective type do you find trickier — い or な? Or maybe you have a question about an exception that confused you? Share in the comments below — your question might help another learner too!

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— **Editor notes**: – Internal links verified via WP REST API: te-form-japanese (post 64877), masu-form-vs-dictionary-form (post 65404), japanese-essential-verbs (post 65425) — all confirmed live. – The article does not include thumbnail images; visual assets are image-planner’s responsibility. – “Adverb” forms (寒く, 静かに) are briefly introduced but not covered deeply — a future article on adverb formation could expand this. – The section on 〜すぎる (too adjective) was considered but held for a separate focused article to avoid scope creep. – Balloon image N values used: Yuka 26, 35, 44; Rei 7, 8, 22 — all within confirmed valid set.

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