N4Grammar

に気(き)が付(つ)く

To notice (that), To realize (that)

Structure

Verb + こと⁽¹⁾ + に気(き)がつく
Noun + に気(き)がつく

⁽¹⁾ の

Explanation

に気(き)が付(つ)く is an everyday phrase used to express becoming aware of or realizing something. The verb 付(つ)く means 'to be attached to', and it happens on its own without a direct action. The case marking particle に is used to indicate the thing to which your 気(き) (awareness or attention) has suddenly become attached.

This grammar pattern is placed after a noun, or a verb phrase that has been made into a noun using either の or こと.

映画館(えいがかん)に着(つ)いて、映画(えいが)がもう始(はじ)まっていたことに気(き)が付(つ)いた。
After I got to the movie theater, I realized the movie had already started.
部屋(へや)の電気(でんき)がつけっぱなしだったのに気(き)が付(つ)いた。
I realized that I'd left the light on in my room.
書類(しょるい)の間違(まちが)いに気(き)が付(つ)いた。
I noticed a mistake in the document.

Fun Fact

The word 気(き) has many possible translations in English, including 'spirit', 'energy', 'feeling', and 'mind'. Its meaning is highly dependent on the context. A useful way to think of 気(き) is as one's 'consciousness' or 'awareness'. In this expression, 気(き) is the awareness that gets drawn to and 'sticks' to something, causing you to notice it.

Examples

何(なん)か変(へん)な音(おと)がしたか気(き)がついただろうか。

I wonder if they noticed that strange sound.

財布(さいふ)を家(いえ)に置(お)いてきたことに気(き)がついたばかりだ。

I just now realized that I left my wallet at home.

文章(ぶんしょう)の間違(まちが)いに気(き)がつきましたか。

Did you notice the mistake in the sentence?

あっ！気(き)がつかなかった！ごめんね！

Oh! I didn't notice! Sorry!

え、もう１２(じゅうに)時(じ)だ！ 気(き)がついていなかった。

What, it's already 12 o'clock! I didn't realize.

店(みせ)がもう閉(し)まっている事(こと)に気(き)がついていなかったです。

I didn't realize that the store was already closed.

僕(ぼく)がメガネをかけていることに気(き)がついた？

Did you notice that I'm wearing glasses?

彼女(かのじょ)は、私(わたし)の声(こえ)の変化(へんか)に気(き)がついてくれた。

She noticed the change in my voice.

夢中(むちゅう)で本(ほん)を読(よ)んでいたから、雨(あめ)が降(ふ)り始(はじ)めたことに気(き)がついていなかった。

I was so absorbed in my book that I didn't notice that it had started raining. (Literally - Wasn't realizing)

窓(まど)の外(そと)を見(み)て、もう暗(くら)くなったことに気(き)がついた。

I looked out the window and realized that it had already gotten dark.

駅(えき)に着(つ)いた時(とき)、携帯(けいたい)を持(も)ってくることを忘(わす)れたことに気(き)がついた。

When I arrived at the station I realized that I forgot to bring my phone.

その映画(えいが)が３時間(じかん)もあると言(い)うことに気(き)がついていなかった。

I didn't realize that this movie was three hours long. (Literally - Wasn't realizing)