What you saw was probably either 가깝다 (close) or 친하다 (be close friends with). 가깝다 has a broader meaning, so can include being close with someone through work functions. But it usually means being close as friends. - 둘이 가까운 사이예요?: Are you two close to each other? - AA 씨와는 3년 전부터 가까이[가깝게] 지냈어요: I've been on close terms with AA for the past three years. (This could mean either business relationship or personal friendship) 친하다 means being close as friends or neighbors, or some other way in private life. - 둘이 친한 사이예요?: Are you two close friends? - AA 씨와는 대학교 때부터 친한 사이였어요: I've been close friends with AA since college days.

I see you are close with him 네가 그 사람하고 친한 걸 알아. They seem to be close 그들은 서로 친한 것 같아. "친하다" means "close (to)" ex) 나는 그와 매우 친하다 I'm good friends with him 앞으로 친하게 지냅시다 I hope we can be good friends from now on. 친할수록 더 예의를 지켜야 한다 The closer you are to someone, all the more respectful you need to be. 나는 이웃들과 별로 친하지 않다 I don't really get along with my neighbors.