이 많아서

because there are many

→ 이

phrase Very common #537

because there are many This is a fragment: 이 marks the preceding noun as the subject, and 많아서 means “because there are many” or “because there is a lot.”

KO: 할 일이 많아서 오늘은 못 가요.

EN: I can’t go today because I have a lot to do.

처음에는 동작이 많아서 그랬던 것 같아.

I think it was because there were a lot of movements at first.

— 극장판 귀멸의 칼날: 무한성편 (2025)

승객이 많아서 멀미 났나 봐

I guess I got motion sick because there were so many passengers.

— 동경 이야기 (1953)

사람이 많아서 기다려야 돼요

There are a lot of people, so we have to wait.

— 중경삼림 (1994)