Video
Let’s watch this short video for a quick overview.
Source: gokigen japanese official YouTube Channel
Introduction
In English, we often say things like:
- “It became cold.”
- “I became a teacher.”
- “It got quiet.”
But how do you say “become” or “get” in Japanese?
In this article, we’ll learn how to express changes or transitions in Japanese using two important grammar structures:
- 〜くなる for い-adjectives
- 〜になる for な-adjectives and nouns
Let’s master how to describe what something or someone has become — naturally and correctly!
1. The Basic Pattern
For い-adjectives (i-adjectives):
Remove the final い, then add くなる.
| Adjective | Becomes… |
|---|---|
| あたたかい | あたたかくなる (become warm) |
| たのしい | たのしくなる (become fun) |
| ねむい | ねむくなる (get sleepy) |
| かわいい | かわいくなる (become cute) |
irregular: いい, かっこいい
| Adjective | Becomes… |
|---|---|
| いい | よくなる (become good, NOT いくなる) |
| かっこいい | かっこよくなる (become cool, NOT かっこいくなる) |
For な-adjectives (na-adjectives):
Remove the final な, then add になる. (Use the adjective stem + になる)
| Adjective | Becomes… |
|---|---|
| しずか（な） | しずかになる (become quiet) |
| しあわせ（な） | しあわせになる (become happy) |
| たいへん（な） | たいへんになる (become difficult/hard) |
For nouns:
Just add になる after the noun.
| Noun | Becomes… |
|---|---|
| 医者 | 医者になる (become a doctor) |
| 看護師 | 看護師になる (become a nurse) |
| 冬 | 冬になる (it becomes winter) |
2. Examples in Action
Using 〜くなる
- 日本語の勉強が楽しくなりました。
= Studying Japanese has become fun. - 冬になると、寒くなります。
= When it becomes winter, it gets cold. - 昨日の夜、寝ませんでした。だから今日、会社で眠くなりました。
= I did not sleep last night. So today, I became sleepy at work.
Using 〜になる
- 練習して、ピアノが上手になりました。
= I have been practicing and getting better at the piano. - メイさんは会社員になりました。
= Mei became an office worker. - 掃除して、部屋がきれいになりました。
= After cleaning, the room became clean.
3. Common Mistakes to Avoid
| Incorrect ❌ | Correct ✅ |
|---|---|
| 便利（な）→ 便利くなる | 便利になる (便利 is a な-adjective) |
| 楽しい → 楽しいになる | 楽しくなる (楽しい is an い-adjective) |
| きれい → きれくなる | きれいになる (きれい is a な-adjective, NOT an い-adjective) |
💡 Tip: Always double-check the adjective type before conjugating!
4. Practice Time!
Change these to “become” sentences:
| Word | Type | Becomes… |
|---|---|---|
| おそい (slow/late) | い-adjective | おそくなる |
| すずしい (cool) | い-adjective | すずしくなる |
| しあわせ（な） | な-adjective | しあわせになる |
| たいへん（な） | な-adjective | たいへんになる |
| 医者 (doctor) | noun | 医者になる |
| 雪 (snow) | noun | 雪になる |
5. FAQ – Frequently Asked Questions
- QCan I use 〜くなる and 〜になる in the past or future tense?
- A
Yes. The verb なる (“to become”) is an u-verb, so it follows the regular u-verb conjugation rules. Because of that, both 〜くなる and 〜になる conjugate the same way as なる itself. Here are the main forms of なる:
- なる (plain present/future)
- なります (polite present/future)
- なって (te-form)
- ならない (plain negative)
- なった (plain past)
- ならなかった (plain past negative)
- QWhat if I’m not sure if it’s a な-adjective or い-adjective?
- A
Check the ending:
- い-adjectives usually end in い (e.g. あたたかい → あたたかくなる)
- な-adjectives do not, and need な before a noun (e.g. しずかな → しずかになる)
- QWhat’s the difference between 〜になる (ni naru) and 〜にする (ni suru)?
- A
- 〜になる (ni naru): Means something becomes, gets, or turns into something naturally or as a result of a process. (Ex: 冬になる – Fuyu ni naru – It becomes winter; 彼は医者になった – Kare wa isha ni natta – He became a doctor).
- 〜にする (ni suru): Means someone decides on something (Ex: コーヒーにする – Koohii ni suru – I’ll have coffee) or actively makes something a certain way (Ex: 部屋をきれいにする – Heya o kirei ni suru – I make the room clean).
- Think: なる = happens, する = someone does/decides.
- QCan I use these forms to talk about becoming able to do something (like “become able to swim”)?
- A
You don’t use 〜くなる or 〜になる directly with verbs for this. To say you “become able to do” something, you use the potential form of the verb followed by 〜ようになる (you ni naru).
Example: 泳げるようになりました (Oyogeru you ni narimashita – I became able to swim). This is a separate but very important pattern!
- QCan 〜くなる / 〜になる express a gradual change over time?
- A
Yes, these forms often describe the result of a change that happened over time. To specifically emphasize that a change is in progress or happening gradually, you can use the 〜てくる (te kuru) form: 〜くなってくる (ku natte kuru) or 〜になってくる (ni natte kuru).
Example: だんだん日本語が上手になってきました (Dandan Nihongo ga jouzu ni natte kimashita – My Japanese has gradually been getting better).
6. Conclusion
Now you can confidently describe change and transformation in Japanese using:
✅ 〜くなる for い-adjectives
✅ 〜になる for な-adjectives and nouns
✅ Real-life examples to express how things or people become something else
🎯 Try this: Write 3 things about how your life has changed since starting to learn Japanese. Use 〜くなった and 〜になった!
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