是不是 (shì bu shì) for Confirmation | Chinese (Mandarin) Grammar

On the surface 是不是 (shì bu shì) is just A-not-A on the copula 是 — and in a sentence like 你是不是学生？ ("are you a student?") that is exactly what it is. But 是不是 has a second, far more useful life: it detaches from the copula and becomes a movable confirmation tag meaning roughly "right? / is it the case that…?" In this role it comments on a whole proposition that already has its own verb, and it can slide to the front, to the middle after the subject, or to the very end — the same three positions English fills with "is it that…", "…, aren't you", and "…, right?" It's how you voice a hunch and ask someone to confirm it.

Three positions, one meaning

The key move to grasp is that 是不是 here does not replace the sentence's real verb. Take a complete statement — 你累了 ("you're tired"), 你忘了 ("you forgot") — and drop 是不是 into one of three slots. The statement's own predicate (累了, 忘了) stays put.

Position	Example	Flavor
Front	是不是你忘了？	strongest — voicing a suspicion, mildly accusing
After subject	你是不是忘了？	neutral — the default confirming check
Final (after comma)	你忘了，是不是？	softest — a tacked-on afterthought

你是不是累了？

nǐ shì bu shì lèi le

You're tired, aren't you? (informal) — 是不是 after the subject; the real predicate is 累了.

是不是你忘了带钥匙？

shì bu shì nǐ wàng le dài yàoshi

Is it that you forgot to bring the keys? (informal) — front position, voicing a suspicion.

你没吃饭，是不是？

nǐ méi chī fàn, shì bu shì

You haven't eaten, right? (informal) — tag on the end, softest of the three.

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Notice 是不是 sits alongside the real verb, never in place of it: 你是不是累了 keeps 累了. That's the whole trick — it's a comment on the proposition, so the proposition still needs its own predicate.

It presupposes a guess

A bare 吗 question is neutral — you genuinely don't know. 是不是 is different: it broadcasts that you already have a guess and you want it confirmed. That's why it feels leading, and why it's the natural tool for reading a situation aloud — spotting that someone looks unwell, sensing that two friends have quarreled, predicting the weather. You're not opening the question from zero; you're checking a hunch.

你脸色不好，是不是病了？

nǐ liǎnsè bù hǎo, shì bu shì bìng le

You look pale — are you sick? (informal) — reading the situation and asking to confirm.

你们是不是吵架了？

nǐmen shì bu shì chǎojià le

Did you two have a fight? (informal) — a hunch about what happened.

明天是不是要下雨？

míngtiān shì bu shì yào xià yǔ

It's going to rain tomorrow, isn't it? (informal) — 是不是 confirming an expectation.

他是不是不想来？

tā shì bu shì bù xiǎng lái

He doesn't want to come, does he? (informal) — the negative proposition 不想来 kept intact.

When 是 really is the main verb

Don't lose sight of the plain case. When you're actually asking about identity or category, 是 is the main verb, and 是不是 is ordinary A-not-A on it — there's no separate predicate. This is the one time 是不是 is followed directly by a noun.

你是不是学生？

nǐ shì bu shì xuésheng

Are you a student? (neutral) — here 是 is the real verb; 是不是 is plain A-not-A.

是不是这个？

shì bu shì zhège

Is it this one? (informal) — pointing at something; 是 is the copula itself.

Common Mistakes

1. Dropping the proposition's own verb. When 是不是 is a confirmation tag, the sentence still needs its real predicate. "Are you tired?" is 累了 (or use plain A-not-A 累不累), not a bare adjective after 是不是.

❌ 你是不是累？

Incorrect — 累 needs its own frame. Say 你是不是累了？ or simply 你累不累？

✅ 你是不是累了？

nǐ shì bu shì lèi le

You're tired, aren't you? (informal) — the real predicate 累了 stays.

2. Adding 吗. 是不是 is already a full question; stacking 吗 on top is ungrammatical.

❌ 是不是你忘了吗？

Incorrect — drop 吗; 是不是 already asks: 是不是你忘了？

✅ 是不是你忘了？

shì bu shì nǐ wàng le

Is it that you forgot? (informal) — one question marker, not two.

3. Doubling up A-not-A. Don't put both 是不是 and an A-not-A on the same predicate; pick one.

❌ 你是不是累不累？

Incorrect — one question strategy at a time: 你累不累？ or 你是不是累了？

✅ 你累不累？

nǐ lèi bu lèi

Are you tired? (informal) — a clean single A-not-A.

4. Splitting the predicate around the tag. As a final tag, 是不是 goes after the whole clause (behind a comma), not wedged into it.

❌ 你累是不是了？

Incorrect — don't break up 累了. Say 你累了，是不是？ or 你是不是累了？

✅ 你累了，是不是？

nǐ lèi le, shì bu shì

You're tired, right? (informal) — the clause stays whole, tag appended.

Key Takeaways

是不是 is a movable confirmation tag — front, after the subject, or final — meaning "right? / is it the case that…?"
As a tag it comments on a whole proposition, so the sentence keeps its own verb: 你是不是累了.
It presupposes your guess and asks for confirmation — softer and more leading than a bare 吗 question.
Position tunes the tone: front = suspicion, after subject = neutral, final = soft afterthought.
When 是 is the actual verb (你是不是学生？), it's just plain A-not-A — and either way, never add 吗.

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