〜になる / 〜くなる: How to Say 'Become' in Japanese
The change なる captures
なる is the verb of things turning into something new — usually on their own, rather than because anyone set out to make it happen. It stretches across people growing into a role (becoming a doctor), the world shifting around you (the cold setting in, a new season arriving), and qualities sliding up or down (getting bigger, getting quieter). Whatever the change, the one decision you have to make is the little connector in front of なる: に or く.
ヤッタンは医者になりたいです。
ヤッタンは いしゃに なりたいです。
Yattan wants to become a doctor.
だんだん寒くなりました。
だんだん さむく なりました。
It has gradually gotten cold.
い-adjective 寒い → 寒くなる.
もうすぐ春になります。
もうすぐ はるに なります。
It will be spring soon.
Noun 春 + に + なる for the change of season.
に or く: reading it off the word in front
The whole pattern comes down to what kind of word なる is attached to. Three cases, and the connector follows automatically:
| Word type | How to connect | Example |
|---|---|---|
| Noun | noun + に + なる | 医者になる (become a doctor) |
| な-adjective | drop な, add に + なる | 元気になる (get well / cheer up) |
| い-adjective | drop い, add く + なる | 大きくなる (get bigger) |
なる itself conjugates like any う-verb: polite なります, past なった (plain) or なりました (polite), negative ならない / なりません ("doesn't become").
When nouns and な-adjectives lead: に
A plain noun just clips に on before なる — handy for careers, seasons, times of day, and any "turns into X" statement.
ヤッタンの弟は来年、大学生になります。
ヤッタンの おとうとは らいねん、だいがくせいに なります。
Yattan's little brother will become a university student next year.
もう夜になりました。
もう よるに なりました。
It's nighttime already.
夜 (noun) + に + なる.
な-adjectives lean on nouns grammatically, so they take the exact same に:
薬を飲んで、元気になりました。
くすりを のんで、げんきに なりました。
I took medicine and got better.
元気 (な-adjective) → 元気になる.
夜は町が静かになります。
よるは まちが しずかに なります。
At night the town gets quiet.
静か (な-adjective) → 静かになる.
When an い-adjective leads: swap い for く
い-adjectives already own their adverb form, so you strip the final い and add くなる — no borrowed に needed. 寒い → 寒くなる, 大きい → 大きくなる.
ヤッタンは前より大きくなりました。
ヤッタンは まえより おおきく なりました。
Yattan has gotten bigger than before.
大きい (い-adjective) → 大きくなる.
The one word to memorise is いい ("good"): it falls back on its old よ- stem, giving よくなる ("get better") — never ×いくなる.
The words that fake being い-adjectives
The reliable trap is a small set of words that end in an い-sound but are grammatically な-adjectives — 上手, 好き, 嫌い, きれい. They take に, not く, so it is 上手になる and 好きになる, never ×上手くなる. Note 大きい → 大きくなる drops its own い but these never do; and don't leave the い on before く (×大きいくなる).
モチは日本語が上手になりたいです。
モチは にほんごが じょうずに なりたいです。
Mochi wants to get good at Japanese.
上手 is a な-adjective, so it takes に — watch out for this one!
先生の話で、日本語が好きになりました。
せんせいの はなしで、にほんごが すきに なりました。
Thanks to the teacher's talk, I came to like Japanese.
好き is also a な-adjective → 好きになる.
なる or する: it happens vs you decide it
The near-neighbour worth pinning down is する in the にする pattern. なる is a state arriving on its own — a natural or gradual drift. する is someone making it so or choosing it. Set 静かになる ("it gets quiet" — it just happens) against 静かにする ("make it quiet / be quiet" — someone acts to keep it down). At a restaurant, コーヒーにする is "I'll go with the coffee" (your call), whereas コーヒーになる would literally mean something turns into coffee. Change happening to the world → なる; someone choosing or causing it → する. Compare 医者になる ("become a doctor") with 医者にする ("make [someone] a doctor / settle on a doctor").
And if you want "gradually reach the point where you can do something" — "I've become able to read kanji" — that has its own dedicated pattern, 〜ようになる, built right on top of なる.
The short version
- なる = become / get / turn into (a natural change of state).
- Noun + に + なる; な-adjective + に + なる; い-adjective drop い + く + なる.
- Polite なります, past なった / なりました.
- いい → よくなる (irregular).
- なる = it happens on its own; する (にする) = someone decides or makes it so.
Practice it
Choose に + なる or く + なる for each word.
＿＿＿に入れるのに最もよいものを選びなさい。
Choose the grammar pattern that best completes the sentence.
この証拠から、彼は犯人ではないということに＿＿＿。
Frequently asked questions
When do I use に and when do I use く with なる?
Nouns and な-adjectives take に (医者になる, 静かになる). い-adjectives drop the final い and take く (寒くなる, 大きくなる).
What's the difference between なる and する?
なる means something becomes a state naturally (静かになる = it gets quiet). する (にする) means someone deliberately makes it so or decides on it (静かにする = make it quiet; コーヒーにする = I'll have the coffee).
How do I say 'get better / improve' with いい?
いい is irregular: it becomes よくなる, not いくなる. For example, 天気がよくなりました ('the weather got better').
Are 好き and 上手 い-adjectives because they sound like they end in い?
No — 好き and 上手 are な-adjectives, so they take に: 好きになる, 上手になる. Don't add くなる to them.
Where 〜になる / 〜くなる fits
Don't confuse it with
- Conditional 〜と · N4 — The と conditional links A to an inevitable result B: 春になると、桜が咲く. Learn the plain-form formation, why B can't be a request, and how it differs from ば/たら/なら.
- で · N5 — The particle で marks where an action happens, the means or tool you use, the material, the cause, and the scope of a superlative. Learn each use and how で differs from に.
- が · N5 — が marks the grammatical subject and introduces new information. Learn how to use が with question words, existence (ある/いる), ability, and likes such as 好き — plus how が differs from は.
- の · N5 — の links nouns (A's B), replaces a noun ('the red one'), turns verbs into nouns (走るのが速い), and softens casual questions (どうしたの?). Learn all four uses.
Once this clicks, go on to
- 〜ようになる · N4 — 〜ようになる describes a change — something that wasn't true or possible before, but now is. Learn the formation, nuance, and see 12 example sentences with a quick practice quiz.
More N5 grammar to explore
Keep going with related patterns at the same level:
- 〜にする — 〜にする means to decide on or choose something (コーヒーにします = I'll have coffee) and to deliberately make X a certain way (静かにする). Learn the pattern and how it differs from なる.
- 〜のが上手 / 〜のが下手 — 上手 (good at) and 下手 (bad at) are な-adjectives. Learn NOUNが上手, VERBのが上手, the が vs を trap, and why you shouldn't call yourself 上手.
- 〜のが好き — 好き means 'like': a thing takes が (音楽が好き). To like doing something, nominalize the verb with の: 読むのが好き. Learn the formation, 大好き/嫌い, and common particle mistakes.
- Past Tense — The plain past た-form means 'did.' It follows the same sound changes as the て-form (just て→た, で→だ): 食べた, 行った, 飲んだ. Learn it by verb group.
- 〜たことがある — 〜たことがある means you have done something before — 日本に行ったことがある. Learn the past-form formation, the negative 〜たことがない (have never), and how it differs from the plain past.
- 〜てみてください — 〜てみる means to do something and see how it goes (try it out). Add ください for 〜てみてください — a friendly 'please give it a try.' Learn the form, conjugations, and casual 〜てみて.