Adjective Conjugation Complete Guide

Adjectives in Japanese do more than just describe nouns — they conjugate just like verbs! This might feel unusual for English speakers, but once you get the hang of it, it becomes a powerful and flexible part of your Japanese skills.

This complete guide breaks it all down simply and clearly. Let’s go!

Two Types of Japanese Adjectives

First, Japanese adjectives fall into two main categories:

い-adjectives (end in い, like たかい “tall/expensive”)
な-adjectives (don’t end in い, like しずか “quiet”)

Note: Some words like きれい (beautiful/clean) look like い-adjectives, but are な-adjectives!

Conjugating い-Adjectives

1. Present Affirmative (is/are)

Add nothing! Use the adjective as-is.
🟢 たかい (It is expensive)

2. Present Negative (is not/are not)

Drop the final い and add くない (plain) or くありません (polite)
🔴 たかくない (It’s not expensive)

3. Past Affirmative (was/were)

Drop the final い and add かった
🟢 たかかった (It was expensive)

4. Past Negative (was not/were not)

Drop the final い and add くなかった (plain) or くありませんでした (polite)
🔴 たかくなかった (It wasn’t expensive)

Form	Conjugation	Example
Present	たかい	This is expensive.
Present Negative	たかくない or たかくありません	This is not expensive.
Past	たかかった	That was expensive.
Past Negative	たかくなかった or たかくありませんでした	That wasn’t expensive.

Conjugating な-Adjectives

Unlike い-adjectives, な-adjectives need to use forms of です (polite “to be”) or だ (plain form) when used with nouns or on their own.

Let’s use しずか (quiet) as our example.

1. Present Affirmative

Add だ (plain) or です (polite)
🟢 しずかだ / しずかです (It is quiet)

2. Present Negative

Add じゃない (plain) or じゃありません (polite)
🔴 しずかじゃない / しずかじゃありません (It’s not quiet)

3. Past Affirmative

Add だった (plain) or でした (polite)
🟢 しずかだった / しずかでした (It was quiet)

4. Past Negative

Add じゃなかった (plain) or じゃありませんでした (polite)
🔴 しずかじゃなかった / しずかじゃありませんでした (It wasn’t quiet)

Form	Plain Style	Polite Style
Present	しずかだ	しずかです
Present Negative	しずかじゃない	しずかじゃありません
Past	しずかだった	しずかでした
Past Negative	しずかじゃなかった	しずかじゃありませんでした

Irregular Adjective: いい (good)

The adjective いい (good) is irregular, and it doesn’t follow the usual い-adjective pattern. Instead, it conjugates as if it were よい (an older form still used in writing).

Form	Conjugation	Example
Present	いい	このカレーはいいです。(This curry is good.)
Present Negative	よくない or よくありません	カレーはよくないです。(The curry isn’t good.)
Past	よかった	きのうのカレーはよかった。(Yesterday’s curry was good.)
Past Negative	よくなかった or よくありませんでした	カレーはよくなかった。(The curry wasn’t good.)

Note: Although we say いい, its negative and past forms use よ!

Quick Tips

You can make both い-adjectives and な-adjectives polite by adding です (except for some casual conversations).
い-adjectives never need な between the adjective and the noun, but な-adjectives do.
- ✔️ たかいビル (tall building)
- ✔️ しずかなまち (quiet town)

Practice Time!

Try conjugating these adjectives:

おいしい (delicious)
げんき (healthy/energetic – な-adjective)
さむい (cold)
ゆうめい (famous – な-adjective)

Can you write out all four conjugations for each?

Final Thoughts

Japanese adjective conjugation may feel strange at first, but with practice, it becomes second nature. Once you’re comfortable with the patterns, you can describe things naturally in any tense or mood — which makes your Japanese sound a lot more fluent!

Keep practicing, and before you know it, you’ll be able to say everything from “It was a beautiful day” to “This coffee is not hot!” with confidence!

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