〜になる / 〜くなる: How to Say 'Become' in Japanese

What it means

なる describes something becoming or turning into a new state — often naturally, on its own, rather than because someone decided to make it happen. You use it to talk about people changing (becoming a teacher), the world changing (it's getting cold, spring is coming), and qualities changing (getting bigger, getting quieter). The trick is choosing the right connector — に or く — based on the word in front of it.

How to form it

Pick the connector based on the word type that comes before なる:

For polite speech use なります; for the past, なった (plain) or なりました (polite). The negative is ならない / なりません ("doesn't become").

Nouns and な-adjectives → に + なる

A noun simply takes に before なる. This covers careers, seasons, times, and any "turn into X" idea.

な-adjectives work the same way — they behave like nouns, so they also take に:

い-adjectives → drop い, add く + なる

For い-adjectives, remove the final い and add くなる. So 寒い → 寒くなる, 大きい → 大きくなる.

One famous exception: いい ("good") becomes よくなる ("get better"), because いい uses the よ- stem when it conjugates.

なる vs する — natural change vs a deliberate choice

These two are easy to mix up. なる means something becomes a state on its own — a natural or gradual change. する (in the pattern にする) means someone makes it that way or decides on it — a deliberate choice. Compare 静かになる ("it gets quiet" — it just happens) with 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 means "I'll go with the coffee" (your decision), while コーヒーになる would mean something literally turns into coffee. When the change is something happening to the world, reach for なる; when someone is choosing or causing it, reach for する.

If you want to talk about gradually reaching the point where you can do something — like "I've become able to read kanji" — that idea has its own pattern, 〜ようになる, which builds on なる.

Common mistakes

1. Using に with い-adjectives. It's 寒くなる, not 寒いになる. Only nouns and な-adjectives take に.
2. Forgetting to drop the final い. 大きい → 大きくなる (drop the い, then add くなる). Don't say 大きいくなる.
3. Treating 好き / 上手 / 元気 as い-adjectives. They end in sounds that look い-ish but are な-adjectives, so they take に: 好きになる, 上手になる.
4. Confusing なる with する. なる = becomes naturally; する (にする) = someone decides or makes it so. 医者になる ("become a doctor") vs 医者にする ("make [someone] a doctor / decide on a doctor").

Quick recap

• 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.

Your turn

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