What is the difference between 은/는 and 이/가?
이/가 marks the grammatical subject and presents information as new. 은/는 marks the topic — what the sentence is about — and often carries contrast or a general statement. The distinction has no English equivalent, which is why it stays difficult long after the forms are memorised.
New information takes 이/가
When something enters the conversation for the first time, or answers a question about who or what, it takes 이/가. When it is already established and you are commenting on it, it takes 은/는.
누가 왔어요? — 친구가 왔어요.
nuga wasseoyo? — chin-guga wasseoyo
Who came? — A friend came.
New information, so 가.
그 친구는 의사예요.
geu chin-guneun uisayeyo
That friend is a doctor.
Already established, so 는.
은/는 carries contrast
Even without a stated comparison, 은/는 often implies one. This is why using it where 이/가 belongs can make a neutral sentence sound pointed.
저는 커피를 좋아해요.
jeoneun keopireul joahaeyo
I like coffee.
Implies: as for me, whatever others like.
김치는 좋아하는데 매운 건 못 먹어요.
kimchineun joahaneunde maeun geon mot meogeoyo
I like kimchi, but I can't eat spicy things.
Explicit contrast.
General truths take 은/는
Statements about a category in general use the topic particle, because you are saying what is true of the thing as a class rather than reporting an event involving it.
고래는 포유류예요.
goraeneun poyuryuyeyo
Whales are mammals.
한국은 아름다워요.
hangugeun areumdawoyo
Korea is beautiful.
Common mistakes
누가 왔어요? — 친구는 왔어요.
친구가 왔어요.
Answering who requires 이/가, because the friend is the new information.
제 이름가 민수예요.
제 이름은 민수예요.
Introducing yourself sets a topic, so 은. Also, 이름 ends in a consonant, so it would take 이 not 가 in any case.
저가 학생이에요.
저는 학생이에요.
저 takes 는. 제가 exists but marks emphasis or a specific answer to who.
Frequently asked questions
Is there a simple rule?
The closest useful one: 이/가 for new information and for answering who or what, 은/는 for what the sentence is about and for general statements. The rule will not resolve every case, and native intuition here comes from volume of exposure rather than from analysis.
Can a sentence have both?
Frequently, and it is often the clearest illustration. 저는 커피가 좋아요 sets me as the topic and coffee as the grammatical subject — literally, as for me, coffee is good.
What happens after a consonant or vowel?
The forms alternate by sound: 은 and 이 after a consonant, 는 and 가 after a vowel. That part is mechanical once you can read hangul.