Whether (or not) — formal with 是否

Structure … 是否 + Verb/adjective

是否 (shìfǒu) is the formal, written version of 是不是: "whether (or not)". 我不知道他是否会来 = "I don’t know whether he’ll come". It goes before the verb and is very common in indirect questions and careful language. It takes no 吗.

Examples

请qǐng问wèn你nǐ是shì否fǒu同tóng意yì？
May I ask whether you agree?
我wǒ不bù知zhī道dào他tā是shì否fǒu会huì来lái。
I don’t know whether he’ll come.
我wǒ问wèn他tā是shì否fǒu需xū要yào帮bāng助zhù。
I asked him whether he needed help.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.