To say something is not what it seems, you negate the copula 是 (shì, "to be") with 不, giving 不是 (bú shì). 我不是学生 ("I'm not a student"), 这不是我的 ("this isn't mine"). The character 是 is one of the first words learners meet, and its negation is refreshingly regular — one form, one rule: 是 is negated only by 不, never by 没. The traps aren't in 是 itself but in overusing it, because English "is/are/am" covers far more ground than Chinese 是. This page draws those boundaries and introduces the contrastive frame 不是…而是.
The basic pattern: 不 + 是 + noun
是 is a linker between two nouns or noun phrases that names an identity: A 是 B means "A is (the same as / an instance of) B." Its negative simply removes that link:
我不是学生，我是老师。
wǒ bú shì xuésheng, wǒ shì lǎoshī
I'm not a student — I'm a teacher. (neutral)
这不是我的，是我朋友的。
zhè bú shì wǒ de, shì wǒ péngyou de
This isn't mine — it's my friend's. (informal)
他不是中国人，是韩国人。
tā bú shì Zhōngguó rén, shì Hánguó rén
He isn't Chinese — he's Korean. (neutral)
Note two things baked into every example. First, 是 keeps its sandhi pronunciation bú shì — because 是 is 4th tone, 不 rises to bú (see 不 sandhi). Second, there is a noun on both sides: 我 / 学生, 这 / 我的, 他 / 中国人. That two-noun shape is the signature of 是 — and the clue to when not to use it.
What 不是 does NOT negate
Because English "be" is so greedy — "he is tall," "she is at home," "I am hungry" — learners over-apply 是. But Chinese uses 是 only for noun-to-noun identity. Three things English handles with "be" take a completely different negation in Chinese:
| To negate… | Use | Example | Not… |
|---|---|---|---|
| identity (是 + noun) | 不是 | 他不是医生 | — |
| a quality (adjective) | 不 + adjective | 他不高 | ✗ 他不是高 |
| a location (在) | 不在 | 他不在家 | ✗ 他不是在家 |
| possession / existence (有) | 没有 | 我没有钱 | ✗ 我不是有钱 |
The reason adjectives reject 是 is that a Chinese adjective is already a verb ("to be tall," "to be expensive") — it doesn't need a separate "be." So the negation attaches straight to it: 不高, not 不是高. See adjectives as stative verbs.
今天不是很冷，你穿这件就行。
jīntiān bú shì hěn lěng, nǐ chuān zhè jiàn jiù xíng
It's not very cold today — this one will do. (informal)
Read that carefully: 不是 is fine here because it negates the whole assessment 很冷 in a softening, "it's not that it's cold" way — but the plain everyday negative is still 今天不冷 (bù lěng), with no 是. Reach for bare 不 + adjective by default.
不是…而是: not X, but Y
不是 is the hinge of Chinese's main corrective structure: 不是 A，而是 B — "it's not A, but rather B." You deny one thing and supply the correction in the same breath:
他不是不想去，而是没时间。
tā bú shì bù xiǎng qù, ér shì méi shíjiān
It's not that he doesn't want to go — it's that he doesn't have the time. (informal)
That second sentence is a small masterclass in negation: 不是 (deny the claim) … 不想 (habit/desire → 不) … 而是 (correction) … 没时间 (existence → 没). Three negators, each doing its own job. A sibling frame, 不是 A 就是 B ("if not A, then B / either A or B"), is covered on the 不是…而是 / 就是 page.
不是…吗: the rhetorical question
Wrap 不是 in a 吗-question and you get a rhetorical effect — not a real question but a pointed reminder, roughly English "Isn't it the case that…?" / "Didn't you…?":
你不是说过了吗？怎么又问？
nǐ bú shì shuō guo le ma? zěnme yòu wèn?
Didn't you already say so? Why are you asking again? (informal)
The speaker isn't seeking information — they're asserting the opposite of the negative, confidently. It's one of the most natural, high-frequency uses of 不是 in conversation.
不是 as a standalone 'no'
Finally, 不是 on its own works as a flat contradiction — "no," "that's not it" — used to correct a wrong assumption before you go on:
不是，你听我说，我不是那个意思。
bú shì, nǐ tīng wǒ shuō, wǒ bú shì nàge yìsi
No — hear me out, that's not what I meant. (informal)
Chinese has no all-purpose "yes/no" word; you answer by echoing or negating the verb of the question. When the question hinges on 是, the "no" answer is simply 不是.
Common Mistakes
1. Putting 是 in front of an adjective. Adjectives are already verbs; they take bare 不.
❌ 他不是高。
Incorrect — an adjective needs no 是; say 他不高.
✅ 他不高。
tā bù gāo
He isn't tall.
2. Negating 是 with 没. 是 is an identity verb, not 有 or an event — it only ever takes 不.
❌ 我没是学生。
Incorrect — there is no 没是; the copula takes 不: 不是.
✅ 我不是学生。
wǒ bú shì xuésheng
I'm not a student.
3. Using 不是 for location. "Not at home" uses 在, negated to 不在 — not 不是在.
❌ 他不是在家。
Incorrect — location uses 在; say 他不在家.
4. Pronouncing bù shì. Because 是 is 4th tone, 不 rises: it's bú shì, not bù shì.
❌ 不是 pronounced bù shì
Incorrect — 是 is 4th tone, so 不 rises to bú: bú shì.
✅ 不是 pronounced bú shì
bú shì
is not — 不 rises before the 4th-tone 是.
Key Takeaways
- Negate identity with 不 + 是: 我不是学生, 他不是中国人. 是 takes only 不 — never 没是.
- 是 links two nouns; don't use 不是 for adjectives (他不高), locations (不在), or possession (没有).
- Always pronounced bú shì — the 不 rises before the 4th-tone 是.
- 不是 A，而是 B = "not X, but Y"; 不是…吗? is a rhetorical "isn't it…?"; bare 不是 = "no, that's not it."
Related Topics
- The Copula 是 (shì): A is BHSK 1 — 是 (shì) links two nouns — 我是学生, 这是我的书. It is ONLY for noun = noun. It is NOT used before adjectives (你很高, never 你是高), NOT for location (在, not 是), and NOT for possession (有). English 'be' fans out into several Chinese patterns; 是 is just one of them.
- 不是 and 不是…而是 (Correcting)HSK 2 — 是 is negated only with 不 → 不是 (bú shì), never 没. The corrective frame 不是…而是… means 'not X but rather Y', and 不是…就是… means 'if not X then Y'. Past non-identity is still 不是 — pastness comes from a time word, not from 没.
- 不是…而是 & 不是…就是HSK 3 — Two paired frames built on 不是: 不是…而是 corrects ('not X, but rather Y' — 不是茶，而是咖啡), while 不是…就是 is disjunctive ('either X or Y, no third option' — 不是加班就是出差). The trap is swapping 而是 and 就是, which reverses correction into exhaustive choice.
- Adjectives Are Stative Verbs (No 是)HSK 1 — A Chinese adjective is a kind of verb — it predicates on its own, with NO copula 是 (shì). 她很高 'she is tall', 天气很好 'the weather is good', 这个太贵了 'this is too expensive' — never *她是高. 高 already means 'to be tall', so 是 has no job; negate with 不 (不高), not 没.