Overview
The topic particle 은/는 and the subject particle 이/가 are two of the most frequently used particles in Korean. They are often the first stumbling block for learners because English has no equivalent distinction. Both can appear to mark the "subject" of a sentence, but they carry very different nuances.
Understanding when to use 은/는 versus 이/가 is essential for sounding natural in Korean. This lesson breaks down the rules, provides clear comparison tables, and gives you plenty of examples to internalize the difference.
Form: How to Choose 은 vs 는 and 이 vs 가
The choice between the two forms within each pair depends on whether the preceding noun ends in a consonant (받침, batchim) or a vowel.
| Condition | Topic Particle | Subject Particle |
|---|---|---|
| After a consonant (받침) | 은 | 이 |
| After a vowel (no 받침) | 는 | 가 |
Examples of form selection:
| Noun | Ends in | Topic | Subject |
|---|---|---|---|
| 나 (na, I — informal) | vowel | 나는 | 내가 (나+가 contracts) |
| 저 (jeo, I — polite) | vowel | 저는 | 제가 (저+가 contracts) |
| 학생 (haksaeng, student) | consonant ㅇ | 학생은 | 학생이 |
| 친구 (chingu, friend) | vowel | 친구는 | 친구가 |
| 책 (chaek, book) | consonant ㄱ | 책은 | 책이 |
| 물 (mul, water) | consonant ㄹ | 물은 | 물이 |
| 커피 (keopi, coffee) | vowel | 커피는 | 커피가 |
Note: 나 + 가 contracts to 내가 (naega), and 저 + 가 contracts to 제가 (jega). These are irregular but extremely common.
Function 1: 은/는 as Topic Marker
은/는 marks the topic of the sentence — the thing you are talking about. It signals "As for X..." or "Speaking of X..." The information is typically already known or established in the conversation.
Key uses of 은/는:
1. Introducing yourself or a general topic:
저는 학생이에요. As for me, I am a student.
한국어는 재미있어요. As for Korean, it is interesting.
2. Contrasting two things:
사과는 좋아해요. 바나나는 안 좋아해요. Apples, I like. Bananas, I don't like.
오늘은 바빠요. 내일은 괜찮아요. Today I'm busy. Tomorrow I'm fine.
3. Generalizations and universal statements:
고양이는 귀여워요. Cats are cute. (cats in general)
겨울은 추워요. Winter is cold. (winter in general)
Function 2: 이/가 as Subject Marker
이/가 marks the subject — the entity performing the action or being described. It signals new information, focus, or an answer to a question. It draws attention to who or what.
Key uses of 이/가:
1. Introducing new or unknown information:
비가 와요. Rain is coming. (It's raining — new information)
친구가 왔어요. A friend came. (someone arrived — news)
2. Answering "who" or "what" questions:
Q: 누가 했어요? (Who did it?) A: 민수가 했어요. (Minsu did it.)
Q: 뭐가 필요해요? (What do you need?) A: 물이 필요해요. (I need water.)
3. With descriptive verbs (adjectives) describing something specific:
이 꽃이 예뻐요. This flower is pretty. (this specific flower)
날씨가 좋아요. The weather is nice. (right now, specifically)
4. Expressing existence with 있다/없다:
시간이 있어요. I have time. (Time exists.)
돈이 없어요. I don't have money. (Money doesn't exist.)
Comparison Table: 은/는 vs 이/가
| Feature | 은/는 (Topic) | 이/가 (Subject) |
|---|---|---|
| Function | Marks topic / theme | Marks grammatical subject |
| Information | Known / old information | New / focused information |
| English equivalent | "As for X..." / "Speaking of X..." | "X is the one that..." |
| Contrast | Yes (A는 ... B는 ...) | No |
| With question words | Not used (누구는 X) | Required (누가, 뭐가) |
| Generalization | Yes (cats are...) | No (this specific cat...) |
| After 받침 | 은 | 이 |
| After vowel | 는 | 가 |
The Same Sentence, Different Nuance
The difference becomes clear when you compare the same noun with each particle:
| Sentence | Meaning | Nuance |
|---|---|---|
| 민수는 학생이에요. | Minsu is a student. | Topic: "As for Minsu, he's a student." |
| 민수가 학생이에요. | Minsu is the student. | Focus: "Minsu is the one who's a student." |
| 날씨는 좋아요. | The weather is nice. | Topic/contrast: "The weather is nice (but maybe something else isn't)." |
| 날씨가 좋아요. | The weather is nice! | New info: "Hey, the weather is nice!" |
| 커피는 마셨어요. | I drank the coffee (at least). | Contrast: implies something else wasn't done. |
| 커피가 맛있어요. | The coffee is delicious. | Focus on the coffee being tasty. |
Common Patterns and Fixed Expressions
Some constructions strongly prefer one particle over the other:
Always 이/가:
- 있다/없다 (existence): 시간이 있어요, 돈이 없어요
- Question words: 누가, 뭐가, 어디가
- 되다 (to become): 의사가 되고 싶어요 (I want to become a doctor)
- 아니다 (to not be): 학생이 아니에요 (I am not a student)
- First mention of something: 어제 친구가 왔어요 (A friend came yesterday)
Always 은/는:
- Self-introduction: 저는 김민수입니다 (I am Kim Minsu)
- Contrast: A는 ... B는 ...
- General truths: 지구는 둥글다 (The Earth is round)
- Negative contrast: 저는 모르겠어요 (As for me, I don't know)
Common Mistakes
| Mistake | Correction | Why |
|---|---|---|
| 누구는 왔어요? | 누가 왔어요? | Question words take 이/가 |
| 저가 학생이에요. | 저는 학생이에요. | Self-introduction uses 은/는 |
| 물는 없어요. | 물이 없어요. | 있다/없다 takes 이/가 |
| 비는 와요. | 비가 와요. | New info (it's raining) takes 이/가 |
Practice Tip
When in doubt, ask yourself: 1. Am I introducing a topic or making a contrast? Use 은/는. 2. Am I giving new information or answering "who/what"? Use 이/가. 3. Am I using 있다/없다 or a question word? Use 이/가.
With practice, the choice becomes intuitive. Pay attention to how native speakers use these particles in dramas, songs, and conversations.