Introduction
为什么 (wèishénme) means "why". It goes after the subject and before the verb — the same adverb slot 也 (yě) and 都 (dōu) occupy. 你为什么不来？(Nǐ wèishénme bù lái?) — Why aren't you coming?
Overview
Structure: Subj. + 为什么 (wèishénme) + Verb ?
| Pattern | Example | Translation |
|---|---|---|
| Subj + 为什么 + V | 你为什么学中文？(Nǐ wèishénme xué Zhōngwén?) | Why do you study Chinese? |
| Subj + 为什么 + 不 + V | 你为什么不来？(Nǐ wèishénme bù lái?) | Why aren't you coming? |
| 为什么 at the front | 为什么？(Wèishénme?) | Why? |
| Answer with 因为 | 因为我很忙。(Yīnwèi wǒ hěn máng.) | Because I'm busy. |
| 因为……所以…… | 因为下雨，所以我不去。(Yīnwèi xià yǔ, suǒyǐ wǒ bú qù.) | It's raining, so I'm not going. |
为什么 (wèishénme) asks for a reason; 怎么 (zěnme) asks in surprise:
- 你为什么不来？(Nǐ wèishénme bù lái?) — Why aren't you coming? A neutral request for the reason.
- 你怎么不来？(Nǐ zěnme bù lái?) — How come you're not coming? You expected the opposite.
- 为什么 (wèishénme) is safe in every situation; 怎么 (zěnme) carries a hint of "that's not what I thought".
- The answer opens with 因为 (yīnwèi) — because.
Examples
你为什么学中文？
Nǐ wèishénme xué Zhōngwén?
Why are you learning Chinese?
你为什么不吃饭？
Nǐ wèishénme bù chī fàn?
Why aren't you eating?
他为什么没来？
Tā wèishénme méi lái?
Why didn't he come?
为什么这么贵？
Wèishénme zhème guì?
Why is it so expensive?
因为我很忙，所以没去。
Yīnwèi wǒ hěn máng, suǒyǐ méi qù.
I was busy, so I didn't go.
你为什么这么高兴？
Nǐ wèishénme zhème gāoxìng?
Why are you so happy?
Usage Notes
- ❌ 你不来为什么？(Nǐ bù lái wèishénme?) — English puts why at either end; Chinese keeps it before the verb.
- 为什么 (wèishénme) is already a question, so no 吗 (ma). ❌ 你为什么不来吗？(Nǐ wèishénme bù lái ma?)
- 为 (wèi) is 4th tone here — wèishénme, not wéishénme.
- Chinese may keep both halves of the pair where English drops one: 因为……所以…… (yīnwèi … suǒyǐ …) — "because …, therefore …". Using both is correct and normal.
- A bare 为什么？(Wèishénme?) is a complete sentence, exactly like the English "Why?"