이/가

이 / 가 — subject particle

Who or what is doing the action — and why it is not the same as 은/는.

New information, focus, existence

Use 이/가 when you introduce or focus the subject: 누가 왔어요? “Who came?” — 민수가 왔어요. Existence verbs 있다/없다 almost always take 이/가: 시간이 없어요.

Learners overuse 은/는 because textbooks introduce it first. If the sentence answers “who/what?”, prefer 이/가.

비가 와요.

biga wayo.

It’s raining.

제가 할게요.

jega halgeyo.

I’ll do it.