Why Korean has two kinds of 'is'
Korean attaches a small particle to a noun to show its role, and the pair that confuses every learner is the topic particle (은/는) and the subject particle (이/가). English has nothing like them, so there is no word to translate them into. They both seem to mark 'the thing the sentence is about', yet they are not interchangeable.
The short version: the topic particle frames what you are talking about, often something already known. The subject particle points to who or what performs the action, often new or specific information. Same noun, different focus.
First, the spelling rule: consonant or vowel
Before meaning, get the form right. Each particle has two shapes depending on whether the noun ends in a consonant or a vowel.
- Topic: 은 after a consonant (책은, the book), 는 after a vowel (저는, as for me).
- Subject: 이 after a consonant (책이), 가 after a vowel (저가 → 제가, the polite I).
- Quick check: look at the last sound of the noun. Consonant ending takes 은 / 이; vowel ending takes 는 / 가.
The topic particle 은/는: 'as for...'
Use 은/는 to set the theme of a sentence, to state general facts, and to draw contrasts. A useful mental translation is 'as for'.
| 저는 학생이에요. | I am a student. As for me → topic 는 |
| 제 이름은 민수예요. | My name is Minsu. 이름 ends in a consonant → 은 |
| 커피는 좋아하지만 차는 안 좋아해요. | I like coffee but I do not like tea. Contrast → 는 on both |
| 한국은 아름다워요. | Korea is beautiful. General statement → 은 |
The subject particle 이/가: new or specific
Use 이/가 to introduce new information, to identify or emphasise who did something, and to answer 'who?' or 'what?'.
| 누가 왔어요? 친구가 왔어요. | Who came? A friend came. New info / answer → 가 |
| 날씨가 좋아요. | The weather is nice. Observation → subject 가 |
| 문제가 있어요. | There is a problem. 문제 ends in a consonant → 이; existence → 가/이 |
| 제가 했어요. | I did it (it was me). Emphasis on who → 제가 |
The classic contrast, side by side
The clearest way to feel the difference is to see the same kind of sentence with each particle. The topic version frames a known theme; the subject version highlights new or identifying information.
| 제 이름은 민수예요. | My name is Minsu. Stating the topic 'my name' |
| 누가 민수예요? 제가 민수예요. | Who is Minsu? I am Minsu. Identifying → 가 / 제가 |
| 코끼리는 코가 길어요. | As for elephants, the trunk is long. Topic (elephant) + subject (trunk) in one sentence |
Pronunciation: the particles and the linking sound
These particles are short, but Korean links the final consonant of the noun into the particle, which changes how it sounds.
- 은 — 'eun', a short 'uh-n'. 는 — 'neun', 'nuh-n'. The vowel is the neutral 'uh' of 'sofa'.
- 이 — 'i', a clean 'ee'. 가 — 'ga', a hard g as in 'go'.
- Linking: 책이 (book + 이) is pronounced 'chaeg-i', the final ㄱ links into the particle as 'g-i', not 'chaek ee'.
- Special note: 저 + 가 becomes 제가, and 나 + 가 becomes 내가. The polite 'I' (저) and casual 'I' (나) both reshape before the subject particle, so learn 제가 and 내가 as set forms.
Mini-drill: 은/는 or 이/가?
Choose the right particle, then check the key. (Watch the consonant-vs-vowel rule too.)
- 1. 저___ 한국 사람이에요. (I am Korean — stating about myself)
- 2. 누구___ 했어요? (Who did it? — asking who)
- 3. 날씨___ 정말 좋아요. (The weather is really nice — observation)
- 4. 김치___ 맵지만 불고기___ 안 매워요. (Kimchi is spicy but bulgogi is not — contrast)
- 5. 책상 위에 책___ 있어요. (There is a book on the desk — existence)
Answer key
- 1. 저는 — vowel ending + topic (about myself). 저는 한국 사람이에요.
- 2. 누가 — 누구 + 가 contracts to 누가 (asking who → subject). 누가 했어요?
- 3. 날씨가 — vowel ending + new observation → subject. 날씨가 좋아요.
- 4. 김치는 / 불고기는 — both take 는 for contrast (vowel endings).
- 5. 책이 — consonant ending + existence → subject 이. 책이 있어요.
Frequently asked questions
What is the difference between 은/는 and 이/가 in Korean?
은/는 is the topic particle: it frames what the sentence is about, often something already known, and works like 'as for'. 이/가 is the subject particle: it points to who or what performs the action, usually new or specific information. The same noun can take either, depending on whether you are setting a theme or highlighting new information.
How do I know whether to add 은 or 는 (and 이 or 가)?
It depends on the final sound of the noun. If the noun ends in a consonant, use 은 (topic) or 이 (subject): 책은, 책이. If it ends in a vowel, use 는 (topic) or 가 (subject): 저는, 날씨가. Check the last letter of the noun first, then choose the matching shape.
Why does 'who' use 가 in 누가 왔어요?
Because a question word like 누구 (who) asks for new, specific information, and new information takes the subject particle 이/가. 누구 plus 가 contracts to 누가. The answer also takes 가: 친구가 왔어요 (a friend came), because the friend is the new information being supplied.
Can a sentence have both a topic and a subject particle?
Yes, and it is very common. 코끼리는 코가 길어요 means 'as for elephants, the trunk is long'. 코끼리는 sets the topic (elephants), and 코가 marks the subject of the description (the trunk). This double structure is a natural and frequent pattern in Korean.