이/가 vs 을/를

설명

이/가 marks the subject (who/what does the action or is described). After a batchim use 이 (책이); after an open syllable use 가 (사과가).

을/를 marks the object of a transitive verb. Batchim → 을 (물을), open → 를 (커피를).

If you can ask “who/what is doing it?” use 이/가. If you can ask “who/what is affected?” use 을/를.

Drill with the same noun: 친구가 와요 (a friend comes) vs 친구를 만나요 (meet a friend).