是不是
Pattern
是不是 + statement？
Key words
Core idea
是不是 asks the listener to confirm a guess. It often feels like the speaker has noticed something and wants to check whether that reading is correct.
The structure can sit before a statement or appear where 是 would normally appear. In both cases, it turns the sentence into a confirmation question.
Placement and tone
Use 是不是 when you are checking an assumption. It is stronger than a plain open question, but still very common in friendly conversation.
Do not add 吗 after it. 是不是 already makes the sentence a question.
At this level, the safest word order is to keep the subject before 是不是. You will also see 是不是 before a whole statement when the speaker is checking an assumption.
Compare with other yes/no questions
吗 asks a neutral yes/no question. A-not-A builds the choice into the predicate. 是不是 often asks, “is my guess right?” That confirmation flavor is the reason it deserves its own page.
Examples
你是不是很累？
Nǐ shì bu shì hěn lèi?
Are you very tired?
The speaker is checking a guess.
他是不是今天来？
Tā shì bu shì jīntiān lái?
Is he coming today?
是不是 can come before the main statement.
这是不是你的书？
Zhè shì bu shì nǐ de shū?
Is this your book?
Common mistakes
Avoid
你是不是很累吗？
Use
你是不是很累？
Do not add 吗 after a 是不是 question.
Avoid
是不是你很累？
Use
你是不是很累？
This beginner pattern is usually safest with the subject before 是不是.