것을 안다

know that

→ 것
phrase Uncommon #8,936
know that Used after a clause to mean knowing that something is the case. 것을 can also refer to a thing or fact, and is often shortened to 걸 in casual speech.
KO: 나는 네가 최선을 다하고 있다는 것을 안다.
EN: I know that you're doing your best.

당신은 내가 결혼한 것을 안다.

You know that I'm married.

우리는 이 남자가 어딘가에 있는 것을 안다.

We know that this man is somewhere on the island.

— 아바타: 물의 길 (2022)