Topic and Subject Particles · 은/는, 이/가

2. How it works

2.1 The basic formula

A particle is attached directly to the noun, with no space. The two pairs are used in the same slot, so you pick one pair for each noun.

Noun + 은/는   →  topic (what we are talking about, or a contrast)
Noun + 이/가   →  subject (new information, or the answer to who/what)

Think of the topic as the title of a conversation. Think of the subject as the thing that the sentence tells us about for the first time.

2.2 Choosing the form

The form depends on the last sound of the noun. If the noun ends in a consonant, use the longer form. If it ends in a vowel, use the shorter form.

책 + 은 → 책은      chae-geun
책 + 이 → 책이      chae-gi
친구 + 는 → 친구는   chin-gu-neun
친구 + 가 → 친구가   chin-gu-ga

Notice how the sound of the consonant moves to the particle. 책은 sounds like chae-geun, not chaek-eun.

2.3 The topic particle 은/는

Use 은/는 when the listener already knows what you mean, or when you introduce yourself or a new theme. It says "as for this thing". It is also the normal choice for facts, names and general statements.

저는 학생이에요.        As for me, I am a student.
한국어는 재미있어요.     Korean is fun.

은/는 can also show contrast. When you say 커피는 좋아해요, it means coffee, yes, but maybe not other drinks. The speaker leaves a small "but" in the air.

2.4 The subject particle 이/가

Use 이/가 when you give new information. It also answers a question with who or what, and it goes with 있다 and 없다 and with simple descriptions. You are saying "this is the thing I mean".

A good rule for beginners is this. If a question word such as 누가 or 뭐가 asks for the answer, the answer uses 이/가.

2.5 Special forms: 저, 나 and 누구

Three common words change their shape before 이/가. Learn them as fixed pieces, because they are used all the time.

저는 학생이에요.     I am a student.   topic
제가 했어요.        I did it.        subject
누가 와요?          Who is coming?

Never say 저가 or 나가 for the subject. The topic form 저는 is always fine. In polite speech, use 저 and 제. You will hear 나 and 내 mostly with close friends.

2.6 Topic first, then subject

The two particles often work together in one conversation. A question uses 이/가 to ask who or what. The answer repeats that thing, and then the next sentence can use 은/는 to say more about it.

누가 왔어요?           Who came?
민수가 왔어요.         Minsu came.        new information
민수는 학생이에요.      Minsu is a student.   now it is the topic

Before 아니다, the thing that is not true takes 이/가: 학생이 아니에요 means I am not a student. This 이/가 marks the complement, not the subject, so do not mix it up with the topic of the sentence.