気【き】

気 means "mind", "attention", "spirit". It hardly ever stands alone: it joins a particle and a verb in fixed phrases about attention, feelings and moods. The particle is part of the phrase, so きをつける気をつける, きがつく気がつく, きになる気になる and きにする気にする are four different things.

気をつける or 気がつく

気をつける is "be careful", something you do on purpose, and the danger takes に. 気がつく, or きづく気づく, is "notice": it happens to you, and what you notice takes に too. A clause takes こと before に.

• × 足元に気がついてください → 足元に気をつけてください

気になる or 気にする

気になる happens to you: something catches your attention or worries you, and it takes が. 気にする is something you do – you mind it, you let it bother you – and it takes を. That is why "don't worry about it" is きにしないで気にしないで.

• × 音を気になる → 音が気になる

気がする

After a clause in the plain form, 気がする gives a hunch: "I have a feeling that". A noun or a な-adjective goes through ような first.

Usage notes

These go beyond the four everyday phrases and 気がする.

気に入る

気に入る is "take a liking to". Liking something you have just seen or received is said in the past, きにはいった気に入った; a liking that lasts is きにはいっている気に入っている. The thing liked takes が or を.

Temper and mood

With が and an adjective or verb, 気 describes someone's temper or mood: きがみじかい気が短い "short-tempered", きがおもい気が重い "dreading something", きがきく気が利く "thoughtful", きがすむ気が済む "be satisfied".