Learn Hardcore Chinese: nǐ zhīdào tā zài nǎr ma?

Chinese leaves question words in the position where the answer would go (wh‑in‑situ). The normal order for locations is Subject + 在 + Place. So the embedded clause is 她在哪儿 (she at where), not 在哪儿她. When you embed it under 你知道 (you know), you get 你知道她在哪儿吗？

If there’s a question word inside, why do we still add 吗 at the end?

Because the outer question is yes/no: “Do you know…?” The wh‑word is inside the clause you may or may not know. So 你知道她在哪儿吗？ is grammatical.

But you cannot put 吗 on a direct wh‑question: 她在哪儿？ is correct; 她在哪儿吗？ is incorrect.

What’s the difference between 哪儿 and 哪里? Which should I use?

Both mean where. Regional preference:

Mainland North (e.g., Beijing): 哪儿 nǎr
Mainland South/Taiwan: 哪里 nǎlǐ They’re interchangeable in meaning. You’ll also see casual 在哪？ in writing. Use 哪 without 儿/里 when it’s before a classifier, e.g., 哪个人？ (which person?)

What is 在 doing here? Is it the progressive marker (“be doing”)?

Here 在 means “to be located at.” It links the subject to a place: 她在学校 (She is at school). As a progressive marker, 在 comes before a verb: 她在吃饭 (She is eating). In 她在哪儿, it’s the location use.

Can I drop 在 and say 你知道她哪儿吗？?

No. You need a verb to connect the subject to a place; that verb is 在. Without it, the clause is incomplete. You can change the verb if the meaning changes:

你知道她住哪儿吗？ (Do you know where she lives?)
你知道她去哪儿了吗？ (Do you know where she went?)

How do I answer this naturally?

Since it’s a yes/no question about your knowledge, answer with:

知道。/ 不知道。 (I know. / I don’t know.) If you do know and want to provide the place:
知道，她在公司。
她在图书馆。 Avoid answering with 是/不是.

What’s the difference between 你知道她在哪儿吗？ and 你知道她在哪儿？ (no 吗)?

With 吗: a pure yes/no question about whether you know.
Without 吗: often functions as an information request—asking you to actually say where she is. In conversation it can sound more direct: “Do you know where she is (tell me)?” Context and intonation decide.

Can I put 吗 after 知道, like 你知道吗她在哪儿?

Not as one sentence. Either:

Keep 吗 at the very end: 你知道她在哪儿吗？ (preferred), or
Split into two sentences: 你知道吗？她在哪儿？

Are there other yes/no patterns besides using 吗?

Yes.

A‑not‑A: 你知不知道她在哪儿？
Tag question: 你知道她在哪儿，对不对？
With 是不是 (more like “Is it the case that…”): 你是不是知道她在哪儿？ (often implies the speaker suspects you know)

Avoid forms like 你知道她在哪儿没有？ for this meaning.

Should I use 知道, 认识, 明白, or 了解 here?

Use 知道 for factual knowledge: 知道她在哪儿 (know where she is).

认识 = be acquainted with a person: 你认识她吗？
明白 = understand (a point/idea): 你明白我的意思吗？
了解 = have a thorough understanding: 我了解她的情况。

Pronunciation tips: How do I say 哪儿, 吗, and the tones in 知道?

哪儿 = nǎr (third tone on nǎ, with -r “erhua” ending). In regions without -r, say 哪里 nǎlǐ.
吗 = neutral tone (light and short).
知道 is commonly pronounced zhīdao with a neutral tone on dao in everyday speech. You’ll also hear fourth tone dào in some dictionaries/regions; the neutral second syllable is very common.

Why 她, not 他? Do they sound different?

They are pronounced the same (tā). In speech there’s no difference. In writing:

她 = she (female)
他 = he (male)
它 = it (things/animals) If gender is unknown in general writing, 他 is often used by default, but use 她 if you mean a specific woman.

How can I make this more polite?

Add a polite opener and/or honorific:

请问，您知道她在哪儿吗？ You can also add a softener: 劳驾, 麻烦您, or a title/name: 请问，李老师，您知道她在哪儿吗？

How do I talk about past or future location?

Add time words or aspect/modal markers:

Past: 你知道她昨天/刚才在哪儿吗？
Future/expected: 你知道她明天会在哪儿吗？
Ongoing search nuance: 你知道她现在在哪儿吗？

Can I use 什么地方 instead of 哪儿/哪里?

Yes: 你知道她在什么地方吗？ Slightly more formal or descriptive; perfectly natural.

What about 呢? Is 她在哪儿呢？ or 你知道她在哪儿呢？ OK?

她在哪儿呢？ is a direct question meaning “Where is she?”, with 呢 adding a softer, searching tone.
In your sentence, don’t combine 呢 and 吗 together. 你知道她在哪儿呢？ is uncommon/awkward; use either 你知道她在哪儿吗？ (yes/no) or 你知道她在哪儿？ (ask for the place).

Is 她在哪？ acceptable without 儿/里?

Yes in casual writing or texting; it’s read as nǎ. For standard writing, prefer 哪儿 (Mainland North) or 哪里 (South/Taiwan).

What’s the literal, word‑by‑word breakdown?

你 you + 知道 know + 她 she + 在 be‑at + 哪儿 where + 吗 yes/no question particle. Literally: “You know she at where (Q)?” meaning “Do you know where she is?”