是不是
shì​bù​shìshì​bú​shìshì​bu​shì HSK1

is or isn't

是不是 shì​bù​shì frequency
is or isn't verb
used to ask for confirmation or to form a direct question about whether something is the case

你是不是还没吃饭？

nǐ shì​bù​shì hái méi chī​fàn?

Have you not eaten yet?

whether or not verb
used to introduce an indirect question or a clause expressing uncertainty between two possibilities

我不知道他是不是已经回家了。

wǒ bù zhī​dào tā shì​bù​shì yǐ​jīng huí​jiā le.

I don't know if he has already gone home.

是不是 shì​bú​shì
is it true that verb
an interrogative phrase used to ask for confirmation or to form a yes-no question, functioning similarly to an auxiliary for asking if something is the case.
是不是 shì​bu​shì
is it (or not) verb
an interrogative phrase used to ask whether something is the case or to seek confirmation.

Frequency
Movie subtitles
13.1 per million appears in 6% of films
Written text
148.1 per million

Details
HSK 3.0
Level 1

Sources
Definitions
CC-CEDICTAI-generated definitions
Frequency data
SUBTLEX-CHBCC Corpus (BLCU)