〜なる: meaning and usage

How to form it

• noun/な-adjective (stem)+に+なる
• い-adjective (-く form)+なる

How it is used

Describes a change, “become”: nouns and な-adjectives add 「に」, い-adjectives take the 「く」 form. 「〜にする」 means someone makes the change. For changes in ability or habit, use 「〜ようになる」.

Examples

1. 彼女はお酒を飲みすぎると、 顔が真っ赤になる。

   When she drinks too much alcohol, her face turns bright red.

2. 妹は来年二十歳になります。

   My younger sister turns twenty next year.

3. 外が暗くなりましたね。

   It's gotten dark outside, hasn't it?

About the example 真っ赤になる uses なる to describe a change of state: her face turns bright red when she drinks too much.