아니에요 / 아닙니다 / 아니야: Negative Copula Forms

Once you know that 아니다 is the copula's negative, the next job is to conjugate it — to deny things politely, formally, casually, and in the past. The good news is that 아니다 is a well-behaved descriptive verb whose stem ends in 니, so the endings attach regularly. The one thing worth savoring first: this same word, said by itself, is also the everyday Korean "no." That coincidence is not trivia — it explains a feature of Korean that startles English speakers, which is that "no" can be marked for tense.

The full paradigm

Here is 아니다 across the speech levels and both tenses. Notice how transparent the assembly is — the stem 아니 never changes shape; only the ending swaps.

The polite 아니에요 and casual 아니야 have common contractions — 아녜요 and 아냐 — heard constantly in speech and fine in casual writing; the full forms are never wrong. Let's take the levels one at a time.

Polite: 아니에요

The everyday polite denial is 아니에요. It ends in the copular ending 에요 (not the regular 아/어요), a leftover of 아니다's historical origin in the copula — which is why you say 아니에요, not ×아니어요. In a full sentence it pairs with an 이/가-marked complement; on its own it works as a polite "no, that's not so."

A crucial spelling note: it is 아니에요, never ×아니예요. The 예 in 친구예요 is a fused copula 이 — but 아니다 has no such noun-final 이 to fuse, so it keeps the plain 에요. This is the mirror image of the trap on the 이에요 / 예요 page: nouns fuse to 예요, 아니다 stays 에요.

Formal: 아닙니다 / 아닙니까?

In 합니다체, the stem 아니 (a vowel stem) takes the formal ending -ㅂ니다, giving 아닙니다; the question is 아닙니까? Just like 입니다, the ㅂ nasalizes to ㅁ before ㄴ, so 아닙니다 is pronounced [아님니다] and romanized animnida, never ×anipnida.

Casual: 아니야 / 아냐

In 반말, the copular casual ending after a vowel stem is 야, so 아니 + 야 → 아니야, commonly squeezed to 아냐. Use it with close friends, younger people, and children.

Do not form the casual by dropping 요 from 아니에요 — ×아니에is not a word. The casual form is a genuinely different shape, 아니야.

Past: 아니었어요

The past inserts 었 into the stem: 아니 + 었어요 → 아니었어요. Spell it with care — it is 아니었어요, not ×아니였어요. The 였 contraction belongs to a vowel-final noun + copula (가수였어요); 아니다's stem is 아니, and 었 attaches directly with nothing to fuse.

The payoff: 아니에요 is also "no," and "no" can be past tense

Beginners meet 아니요 (a slightly fuller variant of 아니에요) on day one as the polite word for "no" — the counterpart of 네 ("yes"). Only later do they discover it is the same word as the copula's negative. That identity is worth pointing out explicitly, because it dissolves something otherwise baffling.

Since "no" is 아니다, and 아니다 conjugates for tense, Korean "no" can be put in the past: 아니었어요 literally means "it was-not (so)," i.e. "that wasn't the case." English cannot inflect the word no; Korean can, because its "no" is a verb.

For the fuller etiquette of 네 / 아니요 — including the famous trap of answering negative questions — see answering with 네 / 아니요.

Common Mistakes

1. Spelling the polite form ×아니예요. 아니다 has no noun-final 이 to fuse into 예; it stays 아니에요.

2. Spelling the past ×아니였어요. The past is 아니었어요; the 였 fusion belongs to vowel-final nouns, not 아니다.

3. Making the casual form by dropping 요. The casual of 아니에요 is 아니야, not ×아니에.

4. Romanizing the formal as "anipnida." The ㅂ nasalizes before ㄴ: [아님니다], animnida.

Key Takeaways

• 아니다 conjugates as a regular descriptive verb: polite 아니에요 (→ 아녜요), formal 아닙니다 / 아닙니까?, casual 아니야 (→ 아냐), past 아니었어요.
• Guard two spellings: 아니에요 (not ×아니예요) and 아니었어요 (not ×아니였어요) — 아니다 has no fusing 이.
• The formal 아닙니다 is pronounced and romanized animnida (ㅂ → ㅁ before ㄴ).
• The casual form is the distinct word 아니야, not 아니에요 minus 요.
• 아니요 is also the everyday "no," which is why Korean "no" can carry tense: 아니었어요, "it wasn't (so)."