# How to Conjugate Japanese Adjectives: い-Adjectives, な-Adjectives, and Irregular Ones
> Japanese adjective conjugation for i-adjectives and na-adjectives explained. Guide with tense forms, te-form, irregular いい, and practical examples.
**URL:** https://migaku.com/blog/japanese/japanese-adjective-conjugation
**Last Updated:** 2025-12-29
**Tags:** fundamentals, vocabulary, phrases, grammar
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Did you know Japanese adjectives conjugate? In English, "happy" stays "happy" whether you're talking about yesterday or tomorrow. But in Japanese, adjectives change their form based on tense, politeness, and whether you're making a positive or negative statement. I'm going to walk you through exactly how to conjugate both types of Japanese adjectives, including the irregular forms that always trip people up. By the end, as a [Japanese learner](https://migaku.com/learn-japanese), you'll be able to describe things in different tenses and connect multiple adjectives together.

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## The two types of Japanese adjectives
Before we get into conjugation, you need to understand that Japanese has two completely different adjective categories. This matters because they conjugate differently.

- **I-adjectives** always end in い (i). These are true adjectives that conjugate on their own without needing a copula. Examples include atsui (<typo lang="ja" syntax="暑[あつ;k2]い"></typo>) meaning "hot," samui (<typo lang="ja" syntax="寒[さむ;k2]い"></typo>) meaning "cold," and takai (<typo lang="ja" syntax="高[たか;k2]い"></typo>) meaning "tall" or "expensive."
- **Na-adjectives** look more like nouns and need な (na) when they modify a noun directly, or です (desu) in polite sentences. Common examples are kirei (きれい) meaning "pretty" or "clean," shizuka (<typo lang="ja" syntax="静[しず;a]か"></typo>) meaning "quiet," and genki (<typo lang="ja" syntax="元気[げんき;a]"></typo>) meaning "healthy" or "energetic."

You might be wondering: if な from a na-adjective is removed, it looks like an i-adjective, right? Nope. The key difference is that na-adjectives don't have that い ending as part of their core form. The い in kirei isn't the same grammatical element as the い in atsui. Na-adjectives behave more like nouns in how they conjugate.

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## I-adjective conjugations: The complete system
I-adjectives are pretty straightforward once you learn the pattern. The い at the end is what changes for different conjugations.

### Present affirmative (Dictionary form)
This is the basic form you'll find in dictionaries. Just use the adjective as-is:

- **atsui** (<typo lang="ja" syntax="暑[あつ;k2]い"></typo>) meaning "hot"
- **takai** (<typo lang="ja" syntax="高[たか;k2]い"></typo>) meaning "tall/expensive"  
- **oishii** (<typo lang="ja" syntax="美味[おい;h,k3]しい"></typo>) meaning "delicious"
- **yasashii** (<typo lang="ja" syntax="優[やさ;h]しい"></typo>) meaning "kind"

In a sentence: <br><typo lang="ja" syntax="今日[きょう;a] は 暑[あつ;k2]い"></typo>。<br>*Today is hot.*

### Present negative
Drop the final い and add kunai (くない):

- **atsukunai** (<typo lang="ja" syntax="暑[あつ,あつい;k2]くない"></typo>) meaning "not hot"
- **takakunai** (<typo lang="ja" syntax="高[たか,たかい;k2]くない"></typo>) meaning "not tall/not expensive"
- **oishikunai** (<typo lang="ja" syntax="美味[おい,おいしい;h,k3]しくない"></typo>) meaning "not delicious"
- **yasashikunai** (<typo lang="ja" syntax="優[やさ,やさしい;h]しくない"></typo>) meaning "not kind"

In a sentence: <br><typo lang="ja" syntax="今日[きょう;a] は 暑[あつ,あつい;k2]くない"></typo>。<br>*Today is not hot.*

### Past affirmative
Drop the final い and add katta (かった):

- **atsukatta** (<typo lang="ja" syntax="暑[あつ,あつい;k2]かった"></typo>) meaning "was hot"
- **takakatta** (<typo lang="ja" syntax="高[たか,たかい;k2]かった"></typo>) meaning "was tall/was expensive"
- **oishikatta** (<typo lang="ja" syntax="美味[おい,おいしい;h,k3]しかった"></typo>) meaning "was delicious"
- **yasashikatta** (<typo lang="ja" syntax="優[やさ,やさしい;h]しかった"></typo>) meaning "was kind"

In a sentence: <br><typo lang="ja" syntax="昨日[きのう;h] は 暑[あつ,あつい;k2]かった"></typo>。<br>*Yesterday was hot.*

### Past negative
This one combines both changes. Drop the い, add kunakatta (くなかった):

- **atsukunakatta** (<typo lang="ja" syntax="暑[あつ,あつい;k2]くなかった"></typo>) meaning "was not hot"
- **takakunakatta** (<typo lang="ja" syntax="高[たか,たかい;k2]くなかった"></typo>) meaning "was not tall/was not expensive"
- **oishikunakatta** (<typo lang="ja" syntax="美味[おい,おいしい;h,k3]しくなかった"></typo>) meaning "was not delicious"
- **yasashikunakatta** (<typo lang="ja" syntax="優[やさ,やさしい;h]しくなかった"></typo>) meaning "was not kind"

In a sentence: <br><typo lang="ja" syntax="昨日[きのう;h] は 暑[あつ,あつい;k2]くなかった"></typo>。<br>*Yesterday was not hot.*

### [Te-form](https://migaku.com/blog/japanese/japanese-te-form-conjugation-guide) for i-adjectives
The te-form lets you connect adjectives or create a reason. Drop the い and add kute (くて):

- **atsukute** (<typo lang="ja" syntax="暑[あつ,あつい;k2]くて"></typo>) meaning "hot and..."
- **yasukute** (<typo lang="ja" syntax="安[やす,やすい;k2]くて"></typo>) meaning "cheap and..."

Example: <br><typo lang="ja" syntax="この レストラン[;a] は 安[やす,やすい;k2]くて 美味[おい;h,k3]しい"></typo>。<br>*This restaurant is cheap and delicious.*

### Ku-form (Adverbial use)
Want to turn an adjective into an adverb? Drop the い and add ku (く):

- **hayaku** (<typo lang="ja" syntax="速[はや,はやい;k2]く"></typo>) meaning "quickly"
- **takaku** (<typo lang="ja" syntax="高[たか,たかい;k2]く"></typo>) meaning "highly/expensively"

Example: <br><typo lang="ja" syntax="速[はや,はやい;k2]く 走[はし;k2]る"></typo>。<br>*To run quickly.*

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## The irregular adjective: Ii (いい)
Here's where things get annoying. The adjective ii (いい) meaning "good" is irregular. When you conjugate it, you actually use forms based on yoi (<typo lang="ja" syntax="良[よ;k1]い"></typo>), the older version of the same word.

- **Present affirmative:** ii (いい) or yoi (<typo lang="ja" syntax="良[よ;k1]い"></typo>) both mean "good"
- **Present negative:** yokunai (<typo lang="ja" syntax="良[よ,いい;k1]くない"></typo>) meaning "not good"
- **Past affirmative:** yokatta (<typo lang="ja" syntax="良[よ,いい;k1]かった"></typo>) meaning "was good"
- **Past negative:** yokunakatta (<typo lang="ja" syntax="良[よ,いい;k1]くなかった"></typo>) meaning "was not good"
- **Te-form:** yokute (<typo lang="ja" syntax="良[よ,いい;k1]くて"></typo>) meaning "good and..."

You'll hear people say ii in conversation, but the conjugations come from yoi. Just memorize this one separately because it doesn't follow the standard pattern.

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## Na-adjective conjugations: Working with desu
Na-adjectives behave differently because they work more like nouns. In polite speech, they use desu (です), and the conjugation happens through the copula, not the adjective itself.

### Present affirmative
Add desu (です) after the adjective:

- **kirei desu** (きれいです) meaning "is pretty/clean"
- **shizuka desu** (<typo lang="ja" syntax="静[しず;a]か です[;a]"></typo>) meaning "is quiet"
- **genki desu** (<typo lang="ja" syntax="元気[げんき;a] です[;a]"></typo>) meaning "is healthy/energetic"
- **benri desu** (<typo lang="ja" syntax="便利[べんり;a] です[;a]"></typo>) meaning "is convenient"

In a sentence: <br><typo lang="ja" syntax="この 部屋[へや;o] は きれい[;a] です[;a]"></typo>。<br>*This room is clean.*

### Present negative
Add dewa arimasen (ではありません) or the casual ja nai (じゃない):

- **kirei dewa arimasen** (きれいではありません) meaning "is not pretty/clean"
- **shizuka ja nai** (<typo lang="ja" syntax="静[しず;a]か じゃ[,じゃ;h]ない"></typo>) meaning "is not quiet" (Casual)

### Past affirmative
Add deshita (でした):

- **kirei deshita** (きれいでした) meaning "was pretty/clean"
- **shizuka deshita** (<typo lang="ja" syntax="静[しず;a]か でし[,でし;a]た"></typo>) meaning "was quiet"
- **genki deshita** (<typo lang="ja" syntax="元気[げんき;a] でし[,でし;a]た"></typo>) meaning "was healthy/energetic"

### Past negative
Add dewa arimasen deshita (ではありませんでした) or ja nakatta (じゃなかった):

- **kirei dewa arimasen deshita** (きれいではありませんでした) meaning "was not pretty/clean"
- **shizuka ja nakatta** (<typo lang="ja" syntax="静[しず;a]か じゃ[,じゃ;h]なかった"></typo>) meaning "was not quiet" (Casual)

### Te-form for na-adjectives
Add de (で) after the adjective:

- **kirei de** (きれいで) meaning "pretty and..."
- **shizuka de** (<typo lang="ja" syntax="静[しず;a]か で"></typo>) meaning "quiet and..."

Example: <br><typo lang="ja" syntax="この 町[まち;o] は 静[しず;a]か で きれい[;a] です[;a]"></typo>。<br>*This town is quiet and pretty.*

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## Tips for learning Japanese adjective conjugation
Here's what actually helped me get comfortable with adjective conjugation:

1. **Practice with real sentences.** Conjugation charts are useful reference tools, but you need to see adjectives working in actual contexts.
2. **Group similar adjectives together.** When you learn a new adjective, immediately practice all four basic conjugations (Present, negative, past, past negative). This builds the pattern into your brain faster than learning them separately.
3. **Don't confuse na-adjectives with nouns.** Yeah, they behave similarly, but they serve different functions. A na-adjective describes qualities, while a noun names things. The grammar overlaps, but the usage differs.
4. **Listen for conjugations in native content.** When you watch Japanese shows or listen to podcasts, you'll hear these conjugated forms constantly. Your brain starts picking up the patterns automatically through exposure.
5. **Remember that i-adjectives conjugate themselves.** Unlike na-adjectives that rely on です for conjugation, i-adjectives change their own endings. This makes them more similar to verbs in some ways.

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## Why adjective conjugation matters for Japanese learners
Learning to conjugate adjectives opens up way more expression in Japanese. You can talk about past experiences, describe what something wasn't like, and connect multiple descriptions smoothly.

The conjugation system also helps you understand Japanese grammar structure better. Once you see how adjectives, verbs, and the copula all work together, the whole language starts making more sense.

Anyway, if you want to practice these conjugations with real Japanese content, Migaku's browser extension and app let you look up words and grammar patterns instantly while watching shows or reading articles. You can see adjectives in their conjugated forms and get instant explanations. There's a 10-day free trial if you want to check it out.

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## FAQs
<accordion heading="Does the adjective come before the noun in Japanese?">Yes, absolutely. When you modify a noun with an adjective, the adjective comes first, just like in English.</accordion>

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## Tackle the difficult part to improve your Japanese from the very start!
For any learner serious about Japanese, adjective conjugation is difficult, but also fundamental, just like verb conjugation. You'll use these forms in basically every conversation. The advice is to start early and learn the rules. Memorize basic patterns and high-frequency vocab from the very start. Then, as you invest more and more time in media consumption and course learning, your brain will gradually internalize the rules you've learned.

> If you consume media in Japanese, and you understand at least some of the messages and sentences within that media, you will make progress. _Period_.

Pick up the rules, and leave the rest to time!