shéi?
Who?
哪个?
Which one?
哪 (nǎ) is a question word meaning "which," and 个 (gè) is a measure word for general objects. Together, 哪个 means "which one?"
哪个人?
nǎge rén?
Which person? — Specifies that the question is about a person.
哪一个?
nǎ yī gè?
Which one? — More formal version.
你想要哪个?
Nǐ xiǎng yào nǎge?
Which one do you want?
我想要那个。
Wǒ xiǎng yào nàge.
I want that one.
Appropriate
Avoid when
You say 哪个 (nǎge?). It is used to ask which one from a set of items.
It is pronounced 'nǎge?' with a falling-rising tone on 'nǎ' and a neutral tone on 'ge'.
哪个 is more colloquial and common in everyday speech, while 哪一个 is slightly more formal.
Tomyo
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