A는 B이다: Identity Sentences | Korean Grammar

The most basic thing you can do in any language is point at something and say what it is. In Korean that sentence is A은/는 B이다 — "A is B." 저는 학생이에요 ("I'm a student"), 이것은 물이에요 ("this is water"). It looks simple, and it is, but three of its features quietly contradict English expectations: the two halves are marked by particles, the verb comes last, and there is no word for "a" or "the" anywhere in it. This page assembles the pattern so those features stop tripping you.

The division of labor

An identity sentence has two nouns and one copula, and each piece has a fixed job:

A (the thing being identified) takes a topic particle 은/는 — or, in the right context, a subject particle 이/가.
B (what A is identified as) takes the copula 이다 directly, glued on.
Word order is A — B — copula: Korean is verb-final (SOV), so the copula, being the predicate, closes the sentence.

저는 학생이에요.

jeoneun haksaeng-ieyo

I'm a student.

이것은 물이에요.

igeoseun murieyo

This is water.

Line the English up against the Korean and the reshuffle is visible: English is "A — is — B" (subject, verb, complement), Korean is "A — B — is" (topic, complement, copula). The word you are tempted to say second (the "is") is the very last thing out of your mouth.

제 이름은 민수예요.

je ireumeun Minsuyeyo

My name is Minsu.

오늘은 월요일이에요.

oneureun woryoirieyo

Today is Monday.

저 사람은 의사예요.

jeo sarameun uisayeyo

That person is a doctor.

Two allomorphies, two independent decisions

Both the particle on A and the copula on B change shape depending on the sound before them — but they do so independently, and beginners who conflate them get tangled. Keep them separate.

A's particle picks its shape from A's final sound: a 받침 (batchim) takes 은, a vowel takes 는.

B's copula picks its shape from B's final sound: a batchim takes 이에요, a vowel takes 예요.

Ends in…	Topic on A	Copula on B (polite)
consonant (batchim)	은 — 이름은	이에요 — 학생이에요
vowel	는 — 저는	예요 — 친구예요

The two choices don't talk to each other. In 제 이름은 민수예요, A (이름) ends in a consonant so it takes 은, while B (민수) ends in a vowel so it takes 예요 — one of each. Decide them one at a time and the "which ending?" panic disappears. The copula side is detailed on the 이에요 / 예요 page.

여기는 우리 집이에요.

yeogineun uri jibieyo

This is our place.

그건 제 가방이에요.

geugeon je gabang-ieyo

That's my bag.

No articles: Korean has no "a" or "the"

English forces you to choose an article — "a student" vs. "the student." Korean has none. 학생이에요 is, all by itself, "am a student" and "am the student"; context supplies whatever definiteness the situation calls for. There is nothing to add and nothing to translate.

이건 사과예요.

igeon sagwayeyo

This is an apple. / This is the apple.

This is a relief, not a gap: you never have to agonize over a/an/the. The trap is the reverse — importing an English article by force. Korean 하나 or 한 means the numeral "one," not the article "a," so 한 학생이에요 does not mean "I'm a student"; it means "I'm one student," which is not what you meant to say.

The one thing that stays fixed: the copula doesn't care which particle A took

Here is the point competitors blur. You can mark A with the topic 은/는 or with the subject 이/가, and the choice genuinely changes the discourse framing — 은/는 sets A up as the topic ("as for A…"), while 이/가 presents A as new information, often answering "who/what is it?" But that choice on A has zero effect on the copula on B. The copula is chosen solely by B's final sound; it never reshapes to match the particle on A.

저는 반장이에요.

jeoneun banjang-ieyo

I'm the class president. (as for me…)

제가 반장이에요.

jega banjang-ieyo

I'm the class president. (I'm the one — new info)

Same B (반장), same copula (이에요), whether A is 저는 or 제가. So treat an identity sentence as two separate decisions: (1) which particle frames A, a discourse choice covered on the topic 은/는 and subject 이/가 pages; and (2) how to end with 이다, a pure sound-based choice. They never interfere.

💡

"Which particle on A?" and "which copula on B?" are independent questions. The particle on A is about framing (topic vs. new info); the copula on B is about B's final sound. Answer them one at a time and you'll never again wonder whether marking A with 가 forces some change on the ending — it doesn't.

Common Mistakes

1. Inserting a word for "a" / "the." Korean has no articles; 한 is the numeral "one," not "a."

❌ 저는 한 학생이에요.

Wrong — this says 'I'm one student.' There's no article in Korean.

✅ 저는 학생이에요.

jeoneun haksaeng-ieyo

I'm a student.

2. Marking B with the object particle. B is a bare noun plus the copula — never object-marked with 을/를.

❌ 이것은 물을 이에요.

Wrong — B takes the copula directly, not an object particle.

✅ 이것은 물이에요.

igeoseun murieyo

This is water.

3. Putting a space before the copula. 이다 glues onto B with no space.

❌ 저 사람은 의사 예요.

Wrong spacing — the copula attaches to the noun.

✅ 저 사람은 의사예요.

jeo sarameun uisayeyo

That person is a doctor.

4. Using the wrong topic-particle allomorph. A consonant-final A takes 은, a vowel-final A takes 는.

❌ 제 이름는 민수예요.

Wrong — 이름 ends in a consonant, so it takes 은.

✅ 제 이름은 민수예요.

je ireumeun Minsuyeyo

My name is Minsu.

Key Takeaways

The identity sentence is A은/는 B이다: A takes a topic (or subject) particle, B takes the copula directly, and the predicate lands last.
Two independent allomorphies: A's particle (은 after a consonant, 는 after a vowel) and B's copula (이에요 after a consonant, 예요 after a vowel) are chosen separately.
Korean has no articles — 학생이에요 is both "a student" and "the student"; don't import "a" as 한.
The particle on A (은/는 vs. 이/가) changes the framing but never the copula on B.

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