English has a whole shelf of "become" verbs — get (get cold), grow (grow up), turn (turn red), go (go bad), come to (come to like) — and choosing between them is a native's tacit knowledge. Japanese collapses all of that into one verb: なる, "to become / come to be." The only thing you have to learn is how a word attaches to なる, and there the rule is beautifully regular: you put the word into its adverbial form and add なる. い-adjectives become 〜く, na-adjectives and nouns become 〜に. That is the entire mechanical core of this page. The subtler, more important half is what なる means: it describes change that happens on its own, with no one making it happen — and that single fact is why it behaves the way it does.
The core pattern: adverb + なる
なる does not attach to a plain adjective. It attaches to the adverbial form — the same form you use to modify a verb. The logic is literal: you are saying the subject "comes-to-be [in a certain way]." 大きく (biggly) + なる (come to be) = "come to be biggly," i.e. get bigger. Once you see なる as needing an adverb, the 〜く / 〜に split stops feeling arbitrary and starts feeling inevitable, because that split is the adverbial form. (For the full adverbial paradigm, see the adverbial form.)
| Word type | Adverbial link |
| Meaning |
|---|---|---|---|
| い-adjective 大きい | 大きく | 大きくなる | get bigger |
| い-adjective 寒い | 寒く | 寒くなる | get cold(er) |
| な-adjective 静か | 静かに | 静かになる | become quiet |
| な-adjective 便利 | 便利に | 便利になる | become convenient |
| noun 医者 | 医者に | 医者になる | become a doctor |
い-adjectives: drop 〜い, add 〜くなる
For an い-adjective, replace the final 〜い with 〜く and add なる. Nothing about the adjective's "size" changes grammatically — Japanese has no comparative -er ending — so 大きい does not turn into a bigger word; it simply describes a state you are now moving into.
暖かくなりましたね。
atatakaku narimashita ne
It's gotten warm, hasn't it.
だんだん寒くなってきた。
dandan samuku natte kita
It's gradually getting colder.
髪が長くなったから、そろそろ切りたい。
kami ga nagaku natta kara, sorosoro kiritai
My hair's gotten long, so I want to cut it soon.
The irregular pair here is いい/よい "good," whose adverbial form is よく (never いく). So "get better / improve" is よくなる.
薬を飲んだら、少し気分がよくなった。
kusuri o nondara, sukoshi kibun ga yoku natta
After I took the medicine, I felt a bit better.
For why いい borrows よ- for all these forms, see いい vs よい.
な-adjectives and nouns: 〜に + なる
na-adjectives and nouns don't use 〜く. Their adverbial link is に. A na-adjective drops its な (静かな → 静か) and adds に; a noun just adds に directly.
この辺も、ずいぶん便利になりましたね。
kono hen mo, zuibun benri ni narimashita ne
This area's gotten really convenient too, hasn't it.
子どもが寝たので、部屋が急に静かになった。
kodomo ga neta node, heya ga kyū ni shizuka ni natta
The kids fell asleep, so the room suddenly went quiet.
日本語が上手になったね。毎日練習してる？
nihongo ga jōzu ni natta ne. mainichi renshū shiteru?
Your Japanese has gotten good! Are you practicing every day?
With a plain noun, 〜になる is how you say someone becomes that thing — the classic use is a future career or a life stage.
大人になったら、何になりたい？
otona ni nattara, nani ni naritai?
When you grow up, what do you want to be?
姉は去年、医者になりました。
ane wa kyonen, isha ni narimashita
My older sister became a doctor last year.
Why なる is intransitive — the change happens by itself
Here is the point that governs everything: なる is intransitive and spontaneous. It reports that a state came about — the weather warmed, the room fell quiet, someone grew up — without saying anyone caused it. This is exactly the opposite of English, where "become" is neutral about agency and we lean on other verbs (make, turn, get X to) when someone is responsible. In Japanese the responsibility question is baked into the verb choice itself. If the change simply occurred, you use なる. If a person deliberately caused it, you switch to する — covered on 〜くする / 〜にする.
Because なる is intransitive, the thing that changes is marked with が (or topic は), never with を. You cannot "を" a なる sentence — there is no object being acted on, only a subject undergoing change.
空が暗くなってきたから、早く帰ろう。
sora ga kuraku natte kita kara, hayaku kaerō
The sky's getting dark, so let's head home soon.
Conjugating なる
なる is a perfectly ordinary godan (u-verb) ending in る. Once the 〜く/〜に link is in place, you conjugate なる itself for tense and politeness — the adjective part never changes again.
| Form | Plain | Polite |
|---|---|---|
| Non-past | 安くなる | 安くなります |
| Past | 安くなった | 安くなりました |
| Negative | 安くならない | 安くなりません |
| Te-form | 安くなって | 安くなって |
A very common combination is 〜くなってくる / 〜くなっていく, which adds a sense of gradual, unfolding change — "come to be" moving toward the speaker in time (くる) or away into the future (いく). 寒くなってきた frames the cold as having crept up on us; 暑くなっていく frames the heat as a trend stretching ahead.
年を取ると、時間が経つのが早くなっていく気がする。
toshi o toru to, jikan ga tatsu no ga hayaku natte iku ki ga suru
As you get older, it feels like time goes by faster and faster.
Common Mistakes
1. Forgetting the adverbial link (the biggest one). なる needs an adverb, so an い-adjective must become 〜く. Attaching なる to the plain 〜い form is the single most frequent error.
❌ 背が高いなりました。
Incorrect — なる attached to the plain form 高い.
✅ 背が高くなりました。
se ga takaku narimashita
I've gotten taller.
2. Dropping the に with na-adjectives and nouns. na-adjectives and nouns take に, not nothing (and not the plain な).
❌ 姉は医者なった。
Incorrect — noun with no に before なる.
✅ 姉は医者になった。
ane wa isha ni natta
My sister became a doctor.
3. Using する for a change that happened on its own. If nobody made it happen, it must be なる. Using する implies a deliberate agent, which sounds wrong for weather, feelings, and the like.
❌ 最近、暖かくしてきた。
Incorrect — implies someone is deliberately warming things up.
✅ 最近、暖かくなってきた。
saikin, atatakaku natte kita
It's been getting warmer lately.
4. Marking the changing thing with を. なる is intransitive; the subject takes が/は, never を.
❌ 部屋を静かになった。
Incorrect — を cannot appear with intransitive なる.
✅ 部屋が静かになった。
heya ga shizuka ni natta
The room became quiet.
5. Keeping the な of a na-adjective. The adverbial form drops な entirely; 静かな → 静かに, not 静かな + に.
❌ 町がにぎやかなになった。
Incorrect — な not dropped before に.
✅ 町がにぎやかになった。
machi ga nigiyaka ni natta
The town has gotten lively.
Key Takeaways
- Attach なる to the adverbial form: い-adjective → 〜く, na-adjective/noun → 〜に. You are literally saying "come to be [adverbially]," which is why the link is not arbitrary.
- なる is intransitive and spontaneous — the change happens by itself, with no agent. Its subject takes が/は, never を.
- なる vs する is the adjective-side of the transitive/intransitive contrast that pervades Japanese verbs. If someone deliberately causes the change, use する instead.
- The adjective never inflects for degree; you conjugate なる (なった, なりました, なって) for tense and politeness.
Now practice Japanese
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Start learning Japanese→Related Topics
- Adverbial Form: 〜く / 〜にN4 — Turning adjectives into adverbs — i-adjectives change 〜い to 〜く (早く走る), na-adjectives add 〜に (静かに歩く) — the same stem that also feeds なる 'become' and する 'make', plus the よく polysemy.
- 〜くする / 〜にする: Make ItN4 — How to express deliberately causing a change with する — い-adjectives take 〜く, na-adjectives and nouns take 〜に — and how it mirrors, and contrasts with, spontaneous なる.
- 自動詞 / 他動詞: Transitivity PairsN4 — Why Japanese splits into intransitive verbs (subject が, happens by itself) and transitive verbs (object を, someone does it) where English usually gets by with a single verb.
- Two Adjective ClassesN5 — Japanese has two structurally different kinds of adjective — い-adjectives that conjugate themselves like verbs, and な-adjectives that are really nouns borrowing the copula — and this single split explains every adjective form you will ever meet.