The Copula 是 (shì): A is B | Chinese (Mandarin) Grammar

是 (shì) is usually the first verb learners meet, and it's easy to get right and easy to overuse. Its one job is to link two noun phrases and assert that one is the other — identity or category: 我是学生 ("I am a student"), 这是我的书 ("this is my book"). The problem is that English "be" does far more than this. English "be" covers I am a student, I am at home, and I am tired with a single word — but Chinese splits those three across three different structures: 是 for noun = noun, 在 for location, and nothing at all before an adjective. Because English fuses them, beginners spray 是 everywhere — and the error 她是高 ("she is tall") is quite possibly the single most common mistake in beginner Chinese. This page nails down where 是 belongs and, just as important, where it absolutely does not.

A 是 B: noun equals noun

Use 是 when the thing on both sides is a noun (or noun phrase) and you're saying the first is the second. Subject + 是 + noun. It equates the two — names an identity, a role, a category, a possessor.

Subject	是	Noun	Meaning
我 (wǒ)	是 (shì)	学生 (xuésheng)	I am a student
他 (tā)	是 (shì)	老师 (lǎoshī)	he is a teacher
这 (zhè)	是 (shì)	我的书 (wǒ de shū)	this is my book
今天 (jīntiān)	是 (shì)	星期一 (xīngqīyī)	today is Monday

我是学生，他是老师。

wǒ shì xuésheng, tā shì lǎoshī

I'm a student, he's a teacher. (neutral) — noun equals noun on both sides.

这是我的书，那是你的。

zhè shì wǒ de shū, nà shì nǐ de

This is my book, that one's yours. (informal) — 是 links a demonstrative to a possessive noun phrase.

Note that 是 doesn't inflect and has no tense — like every Chinese verb, it's one fixed form. It's negated with 不 → 不是 (bú shì, note the tone change on 不), and questioned either with sentence-final 吗 or with the A-not-A form 是不是.

他不是中国人，是韩国人。

tā bú shì Zhōngguó rén, shì Hánguó rén

He's not Chinese, he's Korean. (neutral) — negation is 不是; 是 never takes 没.

你是不是老师？——是，我教数学。

nǐ shì bu shì lǎoshī? — shì, wǒ jiāo shùxué

Are you a teacher? — Yes, I teach maths. (informal) — 是不是 asks; a bare 是 answers 'yes'.

The golden rule: no 是 before an adjective

Here is the rule that matters more than any other on this page. Chinese adjectives do not take 是. To say "you are tall," you say 你很高 (nǐ hěn gāo) — literally "you very tall" — with no verb "to be" anywhere. Saying 你是高 is wrong, full stop.

Why? Because Chinese adjectives are not adjectives-that-need-a-verb the way English ones are. They are stative verbs — they already contain the "be." 高 doesn't mean "tall," it means "to be tall"; 累 doesn't mean "tired," it means "to be tired." So the verb is already there; adding 是 would be like saying "you are be-tall." The word that normally sits in front of the adjective is 很 (hěn) — nominally "very," but in this frame it's a near-empty default linker, not real emphasis. (Two pages go deeper: adjectives are stative verbs and the default 很.)

你今天很漂亮。

nǐ jīntiān hěn piàoliang

You look lovely today. (informal) — adjective predicate, no 是; 很 is the default linker.

今天很冷，多穿点儿。

jīntiān hěn lěng, duō chuān diǎnr

It's cold today — put on more layers. (informal) — 冷 is a stative verb; 今天是冷 would be wrong.

我有点儿累，想早点儿睡。

wǒ yǒudiǎnr lèi, xiǎng zǎo diǎnr shuì

I'm a bit tired, I want to sleep early. (informal) — 累 stands as its own predicate, no copula.

💡

Before you say 是, ask one question: is a NOUN coming next? A student, my book, a teacher, Monday → yes, use 是. Tall, cold, tired, busy (an adjective) → no 是, use 很. At home, on the table (a place) → no 是, use 在. This one check prevents the most common beginner error there is.

There is one honest wrinkle, and it's worth stating plainly rather than pretending the rule has no edges. 是 can appear before an adjective — but only as a stressed, contrastive "it IS so", never in a plain description. 他是很高 means "he is tall (as it happens / I grant you that)," setting up a contrast or conceding a point. This is the emphatic 是, a different construction from the neutral predicate, and in speech that 是 is audibly stressed. The plain sentence "he is tall" is always 他很高, never 他是高.

他是很高，可惜不喜欢打篮球。

tā shì hěn gāo, kěxī bù xǐhuan dǎ lánqiú

He IS tall, it's just a shame he doesn't like basketball. (informal) — stressed, concessive 是; not the neutral 'he is tall'.

是 is not "be at" — location takes 在

The second thing English "be" smuggles in is location: "I am at home." Chinese does not use 是 for this — location is 在 (zài), a separate verb meaning "to be at / located at." Subject + 在 + place.

我在家，你过来吧。

wǒ zài jiā, nǐ guòlái ba

I'm at home, come on over. (informal) — location is 在, never 是.

你的手机在桌子上。

nǐ de shǒujī zài zhuōzi shang

Your phone is on the table. (neutral) — 在 for 'be located at'.

Keeping 是, 在, and 有 apart is a beginner milestone in itself — 是 equates nouns, 在 locates, 有 asserts existence/possession — laid out on 有 vs 是 vs 在 and, for location specifically, 在 as a location verb.

是 for emphasis and confirmation

Beyond linking nouns, 是 has two everyday supporting roles. First, a stressed 是 affirms or confirms — it's the "yes, it's true" of Chinese, and by itself 是 or 是的 answers "yes." Second, the tag 是不是 can be dropped anywhere into a sentence to ask for confirmation — "..., right?" — regardless of what the main verb is.

你是不是忘了带钥匙？

nǐ shì bu shì wàng le dài yàoshi?

You forgot your keys, didn't you? (informal) — 是不是 tags a confirmation onto any sentence.

——你不喜欢他吧？——我是喜欢他，只是有点儿生气。

nǐ bù xǐhuan tā ba? — wǒ shì xǐhuan tā, zhǐshì yǒudiǎnr shēngqì

— You don't like him, do you? — I DO like him, I'm just a bit annoyed. (informal) — stressed 是 affirms the verb against a doubt.

This affirming 是 is also the seed of the 是…的 construction, which frames how, when, where, or by whom something happened — 我是坐地铁来的 ("I came by subway"). It's a whole pattern of its own; here just notice that the same 是 underlies it. Preview: 是…的 emphasis and, more broadly, 是 for emphasis.

我是坐地铁来的，不是开车。

wǒ shì zuò dìtiě lái de, bú shì kāichē

I came by subway, not by car. (informal) — the 是…的 frame stresses the manner; note 是 negates as 不是.

Common Mistakes

1. Putting 是 before an adjective. The number-one beginner error. Adjectives are stative verbs and take 很, not 是.

❌ 她是高。

Incorrect — no 是 before an adjective. Say 她很高.

✅ 她很高。

tā hěn gāo

She's tall. — adjective predicate with default 很, no copula.

2. Using 是 for location. "Be at a place" is 在, not 是.

❌ 我是在家。

Incorrect — location uses 在. Say 我在家.

✅ 我在家。

wǒ zài jiā

I'm at home. — 在 for location.

3. Using 是 for weather or feelings. Same trap as any adjective — 冷, 热, 忙 are stative verbs.

❌ 今天是很冷。

Incorrect (as a plain statement) — 冷 needs no 是. Say 今天很冷.

✅ 今天很冷。

jīntiān hěn lěng

It's cold today. — the adjective is its own predicate.

4. Negating 是 with 没. 是 is negated only by 不.

❌ 他没是我的老师。

Incorrect — 是 never takes 没. Say 他不是我的老师.

✅ 他不是我的老师。

tā bú shì wǒ de lǎoshī

He isn't my teacher. — 不是, with the tone change on 不.

5. Using 是 for possession. "I have a car" is 有, not 是.

❌ 我是一辆车。

Incorrect — 'have' is 有. 我是一辆车 would mean 'I am a car'. Say 我有一辆车.

✅ 我有一辆车。

wǒ yǒu yí liàng chē

I have a car. — possession is 有.

Key Takeaways

是 links two nouns and asserts one is the other: 我是学生, 这是我的书. That is its whole core job.
Never put 是 before an adjective. Adjectives are stative verbs (高 = "to be tall") and take 很, not 是 — 你很高, never 你是高. This is the most common beginner error.
Location is 在, not 是 (我在家); possession is 有, not 是 (我有车). English "be" splits across 是 / 在 / 有.
是 is negated only by 不 → 不是 (never 没), and questioned with 吗 or 是不是.
A stressed 是 affirms or confirms ("it IS so"), tags a sentence via 是不是, and seeds the 是…的 construction — the one context where 是 may precede an adjective, and only for contrast.

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