미리 is beforehand, in advance etc.. doing something before some events happen. ex) 미리 자리를 잡아두다 reserve a seat beforehand 넌 미리 나에게 말을 했어야 했다 You should have told me beforehand. 짐은 미리 보내라. Send your baggage in advance. 먼저 earlier.before... first or earlier at sequence ex) 내가 그보다 먼저 왔다 I came earlier than he did. / I arrived before he did. 먼저 도착하는 순서대로 나오다. First come, first served. 중요한거 먼저 해라! Do important thing first!