Lesson one teaches 吗 (ma) as the spoken question mark: stick it on the end of a statement and you have a yes/no question — 你是学生吗？ It works so cleanly that learners bolt it onto every question they build, including ones that already ask: 你去哪儿吗？, 你是不是学生吗？ But a sentence containing 哪儿, 谁, 什么, 怎么, an A-not-A verb, or a 还是 choice is already a question. Adding 吗 asks twice. The rule is simple once you see why it exists — 吗 needs a plain statement to convert, and these sentences aren't plain statements.
吗 is the yes/no marker — and only that
吗 does exactly one job: it converts a declarative statement into a question expecting yes or no. For it to work, there has to be a statement underneath.
你是学生吗？
nǐ shì xuésheng ma
Are you a student? (neutral) — 吗 turns the statement 你是学生 into a yes/no question.
这是你的手机吗？
zhè shì nǐ de shǒujī ma
Is this your phone? (neutral) — a plain statement plus 吗.
A question word already makes it a question
谁 (who), 什么 (what), 哪儿 (where), 怎么 (how), 为什么 (why), 几 / 多少 (how many) each turn the sentence into an information question by themselves. The question lives in that word — so 吗 has nothing left to do, and adding it is wrong.
❌ 你去哪儿吗？
Incorrect — 哪儿 already asks 'where'; drop the 吗.
✅ 你去哪儿？
nǐ qù nǎr
Where are you going? — the question word 哪儿 carries the question.
❌ 你叫什么名字吗？
Incorrect — 什么 already asks 'what'.
✅ 你叫什么名字？
nǐ jiào shénme míngzi
What's your name? — 什么 does the asking.
❌ 他是谁吗？
Incorrect — 谁 already asks 'who'.
✅ 他是谁？
tā shì shéi
Who is he? — 谁 carries the question.
A-not-A is a question too
The A-not-A pattern (是不是, 去不去, 好不好) builds the yes/no question straight into the verb, so it also rejects 吗.
❌ 你是不是学生吗？
Incorrect — 是不是 is already the yes/no question.
✅ 你是不是学生？
nǐ shì bu shì xuésheng
Are you a student (or not)? — A-not-A needs no 吗.
❌ 明天你去不去吗？
Incorrect — 去不去 already asks the yes/no.
✅ 明天你去不去？
míngtiān nǐ qù bu qù
Are you going tomorrow? — A-not-A carries it.
Choice questions with 还是 don't take 吗 either
还是 (or) already frames a question offering options, so 吗 would clash.
❌ 你喝茶还是咖啡吗？
Incorrect — 还是 already sets up the choice question.
✅ 你喝茶还是咖啡？
nǐ hē chá háishì kāfēi
Do you want tea or coffee? — 还是 offers the two options.
| Question type | Example | Take 吗? |
|---|---|---|
| yes/no | 你是学生吗？ | ✅ needs 吗 |
| question word | 你是谁？ | ❌ no 吗 |
| A-not-A | 你是不是学生？ | ❌ no 吗 |
| choice with 还是 | 你喝茶还是咖啡？ | ❌ no 吗 |
The one real exception: indefinite 什么 / 谁
Here is the subtlety worth understanding rather than just memorizing. Words like 什么 and 谁 have a second life as indefinites — "something / anything," "someone / anyone." In that meaning they are not the question, so 吗 can legitimately appear:
你想喝点什么吗？
nǐ xiǎng hē diǎn shénme ma
Do you want anything to drink? (informal) — here 什么 means 'anything', so 吗 asks the yes/no.
Compare 你想喝什么？ ("What do you want to drink?", an information question). So 吗 next to 什么 is not automatically wrong — but it flips your meaning from "what specifically?" to "anything at all?" If you wanted the information question, the 吗 is still the wrong tool.
For the yes/no particle in full, see the particle 吗; the whole set of question words at question words overview; the A-not-A pattern at A-not-A questions; 吗 vs question words compared at 吗 vs question words; and choice questions at 还是 choice questions.
Common Mistakes
1. question word + 吗 — the headline.
❌ 现在几点吗？
Incorrect — 几点 already asks 'what time'.
✅ 现在几点？
xiànzài jǐ diǎn
What time is it now? — 几 carries the question.
2. A-not-A + 吗.
❌ 这个菜好不好吃吗？
Incorrect — 好不好吃 is already the yes/no question.
✅ 这个菜好不好吃？
zhège cài hǎo bu hǎochī
Is this dish tasty? — A-not-A, no 吗.
3. 还是 + 吗.
❌ 你去还是他去吗？
Incorrect — 还是 already frames the choice.
✅ 你去还是他去？
nǐ qù háishì tā qù
Are you going, or is he? — 还是 offers the options.
4. 为什么 + 吗.
❌ 你为什么不来吗？
Incorrect — 为什么 already asks 'why'.
✅ 你为什么不来？
nǐ wèishénme bù lái
Why aren't you coming? — 为什么 carries the question.
Key Takeaways
- 吗 converts a statement into a yes/no question — it needs a plain declarative to attach to.
- A sentence with 谁 / 什么 / 哪儿 / 怎么 / 为什么 / 几 / 多少 is already a question; adding 吗 is doubling up.
- A-not-A (是不是, 去不去) and 还是 choice questions are also already questions — no 吗.
- The exception: 什么 / 谁 as indefinites ("anything / anyone") can take 吗 — but that gives a yes/no meaning, not the information question you likely intended.
- Two ways to ask, one per sentence: 吗 or a question marker, never both.
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- A-not-A Questions (是不是, 去不去)HSK 1 — A second neutral way to ask yes/no: juxtapose the positive and negative of the verb or adjective — 去不去, 好不好, 是不是. The middle 不 is toneless, 有 uses 没 (有没有), and you never add 吗.