shéi?
Who?
在哪里?
Where is it?
在 (zài) means "at" or "in," and 哪里 (nǎlǐ) means "where." Together, they form a question meaning "where is it?" The question mark is used in writing, but in speech, intonation rises.
你在哪里?
nǐ zài nǎlǐ?
Where are you? — More personal and conversational, explicitly includes the subject 'you'.
这里是哪里?
zhè lǐ shì nǎ lǐ?
Where is this place? — Clarifies the location of the current place, more specific.
你在哪里?
nǐ zài nǎlǐ?
Where are you?
我在学校。
wǒ zài xuéxiào.
I am at school.
Appropriate
Avoid when
You say '在哪里?' (zài nǎlǐ?). The subject is often omitted if it is clear from context.
It is pronounced 'zài nǎlǐ?' with a rising intonation at the end to indicate a question.
Use it when you want to know the location of something or someone. It is neutral in formality and can be used in most situations.
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