이다 is Korean's "to be [X]" — the word that says A is B (저는 학생이다, "I am a student"). But it is not a free-standing verb the way English is is. 이다 is a bound ending: it attaches directly to the noun in front of it, written as one unit (학생이다, not ×학생 이다), and — this is the part that trips everyone — its shape is triggered by the final sound of that noun. After a consonant-final noun it stays 이-; after a vowel-final noun the 이 fuses into the ending and often vanishes. This page lays out the whole paradigm organized by that consonant/vowel split, so you can look up any cell and get the batchim right the first time.
The paradigm: consonant-final vs vowel-final noun
The columns are the noun type. Throughout, the consonant-final example is 학생 ("student") and the vowel-final one is 친구 ("friend").
| Level / Tense | After consonant-final noun (학생) | After vowel-final noun (친구) |
|---|---|---|
| 합니다체 (formal), present | 학생입니다 (haksaeng-imnida) | 친구입니다 (chingu-imnida) |
| 해요체 (polite), present | 학생이에요 (haksaeng-ieyo) | 친구예요 (chinguyeyo) |
| 반말 (intimate), present | 학생이야 (haksaeng-iya) | 친구야 (chinguya) |
| 한다체 (plain), present | 학생이다 (haksaeng-ida) | 친구다 (chinguda) |
| 해요체, past | 학생이었어요 (haksaeng-ieosseoyo) | 친구였어요 (chinguyeosseoyo) |
| 합니다체, past | 학생이었습니다 (haksaeng-ieotseumnida) | 친구였습니다 (chinguyeotseumnida) |
| 해요체, question | 학생이에요? (haksaeng-ieyo) | 친구예요? (chinguyeyo) |
| 합니다체, question | 학생입니까? (haksaeng-imnikka) | 친구입니까? (chingu-imnikka) |
Where the columns split — and where they don't
Read down the two columns and you will see the split is not everywhere. It is decided by whether the ending starts with a vowel that the noun-final 이 can fuse into.
- 합니다체 (입니다, 입니까) — no split. Because 이 is followed by the consonant ㅂ, there is nothing for a preceding vowel to fuse with, so both columns keep the full 이: 학생입니다 and 친구입니다. This is the one register where you never have to think about the batchim.
- 해요체 present — the split is sharp. After a consonant it is 이에요 (학생이에요); after a vowel the 이 + 에 contracts to 예, giving 예요 (친구예요). This is the copula's most-used and most-misspelled form.
- 반말 present — same split. Keep 이야 after a consonant (학생이야), drop to 야 after a vowel (친구야).
- 한다체 present — same split. 이다 after a consonant (학생이다), bare 다 after a vowel (친구다, 의사다).
- Past — same split. 이었- after a consonant (학생이었어요), contracted 였- after a vowel (친구였어요).
Present, in use
저는 회사원이에요.
jeoneun hoesawonieyo
I'm an office worker. (consonant-final 회사원 → 이에요)
저분은 제 선배예요.
jeobuneun je seonbaeyeyo
That person is my senior. (vowel-final 선배 → 예요)
여보세요, 저예요.
yeoboseyo, jeoyeyo
Hello, it's me. (on the phone; 저 + 예요, contracted after a vowel)
여기가 저희 사무실입니다.
yeogiga jeohui samusirimnida
This is our office. (합니다체 — no split, 입니다)
Past, in use: 이었어요 / 였어요
The past copula is 이었- / 였-, and it obeys the identical split. This is one of the most common everyday forms — talking about what something was.
그때 저는 대학생이었어요.
geuttae jeoneun daehaksaeng-ieosseoyo
Back then I was a university student. (consonant-final → 이었어요)
제 첫 직업은 요리사였어요.
je cheot jigeobeun yorisayeosseoyo
My first job was a cook. (vowel-final 요리사 → 였어요)
The casual and plain forms
너 대학생이야?
neo daehaksaeng-iya
Are you a university student? (반말, consonant-final → 이야; rising intonation = question)
이거 네 거야?
igeo ne geoya
Is this yours? (반말, vowel-final 거 → 야)
As with the whole 반말 system, a copula statement and its yes/no question are the same words — 학생이야 flat is "you're a student," 학생이야? rising is "are you a student?" Nothing reorders; only the pitch (and the question mark) moves.
Don't confuse 이다 with 있다 — or with 아니다
Two neighbors cause endless trouble, so fix the boundaries now.
- 이다 = "is [X]" — identity/definition, glued to a noun: 이건 물이에요 ("this is water"). Its negative is the separate word 아니다 ("is not"): 이건 물이 아니에요.
- 있다 = "exists / there is / has" — a full, free-standing verb, not the copula: 물이 있어요 ("there is water / I have water"). Its negative is 없다. See 있다: existence.
English blurs both under "be," which is exactly why learners say ×저는 시간이에요 for "I have time" (it should be 시간이 있어요). 이다 tells you what something is; 있다 tells you that something exists.
저는 학생이 아니에요.
jeoneun haksaeng-i anieyo
I'm not a student. (negative copula 아니다 — note 아니에요, never ×아니예요)
Common Mistakes
1. Failing to contract after a vowel (×친구이에요). After a vowel-final noun the 이 fuses to 예: 친구예요.
❌ 제 친구는 가수이에요.
Wrong — after a vowel it contracts: 가수예요.
✅ 제 친구는 가수예요.
je chinguneun gasuyeyo
My friend is a singer.
2. Wrongly contracting after a consonant (×학생예요). After a batchim you keep the full 이에요.
❌ 저는 학생예요.
Wrong — 학생 ends in a consonant, so it's 학생이에요.
✅ 저는 학생이에요.
jeoneun haksaeng-ieyo
I'm a student.
3. Spelling the vowel-final form 에요 instead of 예요. The vowel-final copula carries the fused 이 (예) — the #1 copula spelling error.
❌ 그건 우유에요.
Wrong spelling — after a vowel it's 예요: 우유예요.
✅ 그건 우유예요.
geugeon uyuyeyo
That's milk.
4. Using 이다 for "there is / to have" (should be 있다). 이다 is identity, not existence.
❌ 저는 지금 시간이에요.
Wrong verb — 'I have time' is existence: 시간이 있어요.
✅ 저는 지금 시간이 있어요.
jeoneun jigeum sigani isseoyo
I have time right now.
5. Keeping 이 in the casual form after a vowel (×친구이야). The vowel-final 반말 copula drops to 야.
❌ 쟤가 내 친구이야.
Wrong — after a vowel the casual copula is just 야: 친구야.
✅ 쟤가 내 친구야.
jaega nae chinguya
That kid is my friend.
Key Takeaways
- 이다 is a bound ending on the noun, and its shape is triggered by the noun's final sound — not a free-standing "is."
- 해요체 present: 이에요 after a consonant (학생이에요), contracted 예요 after a vowel (친구예요) — spell it 예, never ×에요.
- 합니다체 (입니다/입니까) does not split — the following ㅂ blocks fusion, so both noun types keep 이.
- Past splits identically: 이었- / 였- (학생이었어요 / 친구였어요); 반말 splits 이야 / 야.
- Keep 이다 (identity) apart from 있다 (existence, a separate verb) and 아니다 (the negative copula — 아니에요, not ×아니예요).
Now practice Korean
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Korean→Related Topics
- 아니다 (to not be): Negative Copula ParadigmTOPIK 1 — The full look-up paradigm of 아니다, the suppletive negative copula 'is not [X]' — you never negate 이다 with 안 — laid out across all four speech levels, with the one structural fact that trips everyone up: the complement noun takes the subject particle 이/가, not an object marker.
- 있다 (to exist / to have): Full ParadigmTOPIK 1 — The complete look-up paradigm of 있다 — Korean's one verb for both 'there is / is at' and 'I have' — across all four speech levels, with the crucial detail that it takes the verbal -는 attributive (있는, never ×있은), which is exactly why it's 재미있는, not ×재미있은.
- 해요체: The Informal-Polite Conjugation TableTOPIK 1 — The reference table for 해요체, the default everyday polite register: stem + 아/어 by harmony + 요. One ending -아/어요 serves statement, question, and suggestion — intonation disambiguates. The register where the vowel contractions (와요, 줘요, 마셔요, 돼요, 해요) really bite.
- 이에요 / 예요: Polite Present (with Casual 이야/야)TOPIK 1 — The everyday polite copula picks its shape from the noun's final sound — 이에요 after a consonant, 예요 after a vowel — and the number-one spelling trap is writing 에요 for 예요; the casual 반말 pair 이야/야 tracks it exactly.
- 입니다 / 입니까: The Formal CopulaTOPIK 1 — 입니다 is the formal-polite (합니다체) 'is' of announcements, presentations, and first meetings — it attaches identically to every noun regardless of batchim, its question form is 입니까?, and it is pronounced (and romanized) imnida, never ipnida.