～くなる
becoming a state
～くなる describes a change of state with i-adjectives. Take an i-adjective, change the final い to く, and add なる (to become).
In English it matches “to become ~” or “to get ~”: to get cold, to become fun, to get better.
1. A simple change
Use ～くなる to say that something changed from one state to another. The thing that changes is usually marked with が.
日本語が楽しくなりました。
“Japanese has become fun.”
- 日本語（にほんご）= Japanese (language)
- が = subject marker
- 楽しくなりました（たのしくなりました）= became fun
2. A gradual, ongoing change
To show that a change has been happening over time and is still continuing, combine it with ～てくる: ～くなってきた means “has been getting ~”.
最近、寒くなってきた。
“It’s been getting cold lately.”
- 最近（さいきん）= lately, recently
- 寒くなってきた（さむくなってきた）= has been getting cold (寒くなる plus ～てくる in the past)
How to form it
i-adjective (い → く) + なる. For na-adjectives and nouns, use になる instead (静かになる = to become quiet).
- 寒い（さむい）= cold → 寒くなる（さむくなる）= to get cold
- 高い（たかい）= high, expensive → 高くなる（たかくなる）= to go up, get more expensive
- いい = good → よくなる = to get better (irregular: いい changes to よく)
Key idea
なる means “to become”, and the く-form lets an i-adjective attach to it. Whenever something turns colder, bigger, easier, or better, Japanese says it with ～くなる.
Other N5 grammar
Updated .