为什么 vs 干嘛 (wèishénme vs gànmá): formal vs colloquial 'why'
Both 为什么 and 干嘛 mean 'why', but they differ in register. 为什么 is neutral and standard, suitable for all contexts including formal writing and speech. 干嘛 is highly colloquial, used in casual conversation, often carrying a tone of surprise, mild irritation, or a 'what for?' implication. 干嘛 can also double as a verb phrase meaning 'do what' (e.g., 你干嘛？ = 'What are you doing?').
The core difference between 为什么 and 干嘛 lies in register and tone. 为什么 is the standard, neutral interrogative for 'why,' appropriate in all situations from formal essays to everyday speech. 干嘛, a contraction of 干什么 (gàn shénme, 'do what'), is strongly colloquial and informal; it is common in spoken Mandarin among friends or in casual settings, and often implies a sense of annoyance, curiosity, or 'what's the point?' In addition to meaning 'why,' 干嘛 can also function as a verb phrase meaning 'do what' (e.g., 你在干嘛？ = 'What are you doing?'). Choosing between them depends on the social context and the nuance you want to convey.
When to use each
Use 为什么 in any context where you need a neutral, standard 'why'. It is required in formal writing (essays, reports), professional communication, and serious questions. It is also fine in everyday speech, though it may sound slightly more deliberate than 干嘛.
Use 干嘛 in casual, informal spoken situations, especially with friends, family, or in social media. It often carries a tone of surprise, impatience, or a rhetorical 'what for?' Also use 干嘛 to ask 'what are you doing?' (你干嘛？). Avoid it in formal writing or professional settings.
干嘛 is a contraction of 干什么 (gàn shénme), so it can be literally parsed as 'do what.' When used as 'why,' it retains a slightly accusatory or emotionally charged feel compared to the neutral 为什么.
At a glance
| 为什么 | 干嘛 | |
|---|---|---|
| Register | Formal / Neutral | Informal / Colloquial |
| Typical Context | Writing, interviews, polite questions | Casual chat, texting, complaints |
| Emotional Tone | Neutral, polite | Often surprised, annoyed, or impatient |
| Additional Meaning | Only 'why' | Also 'do what' (e.g., 你干嘛？ = 'What are you doing?') |
| Grammatical Structure | Standard adverb + question particle (为什么) | Derived from verb-object phrase (干 + 嘛); can stand alone as a predicate |
Examples
- 为什么你为什么不去？Nǐ wèishénme bù qù?Why aren't you going?Neutral question; appropriate in any context.
- 干嘛你干嘛不去？Nǐ gànmá bù qù?Why aren't you going? (casual, possibly annoyed)Colloquial; implies the speaker is frustrated or surprised.
- 干嘛你干嘛？Nǐ gànmá?What are you doing? / Why (are you doing that)?Ambiguous; context clarifies if it means 'do what' or 'why.'
- 为什么为什么你要学中文？Wèishénme nǐ yào xué zhōngwén?Why do you want to learn Chinese?Formal or neutral inquiry.
- 干嘛你干嘛学中文？Nǐ gànmá xué zhōngwén?Why (on earth) are you learning Chinese? (casual, curious)Tone: light-hearted or surprised, not suitable for serious discussion.
Common mistakes
- Using 干嘛 in formal writing (e.g., essays, business emails) — always use 为什么.
- Using 为什么 in very casual situations where 干嘛 would sound more natural and friendly, e.g., 你为什么不来？ sounds stiff if you're chatting with a close friend.
- Confusing 干嘛 with 干什么 in writing: 干嘛 is the spoken contraction; in formal writing, use 干什么 or 为什么.
- Thinking 干嘛 cannot mean 'do what' — it does, and that usage is very common in spoken Chinese.
FAQ
- When do I use 为什么 vs 干嘛?
- Use 为什么 for neutral or formal 'why' (writing, polite conversation). Use 干嘛 in casual speech with people you know well, especially when you want to express surprise, annoyance, or a 'what for?' nuance. In formal contexts, only 为什么 is correct.
- Can 干嘛 and 为什么 be used interchangeably?
- Not always. In informal spoken Chinese, they can often be swapped without changing the meaning (though tone differs). However, 干嘛 has an extra meaning ('do what') and is inappropriate in formal situations. 为什么 is always safe but may sound too formal in casual chat.
- Is 干嘛 short for 干什么?
- Yes. 干嘛 is the contracted form of 干什么 (gàn shénme). In casual speech, 干嘛 is used both as 'why' (你为什么不来？ → 你干嘛不来？) and as 'do what' (你干嘛？ = 你干什么？). In writing, the full form 干什么 is more common for the verb phrase.
- Does 干嘛 always sound angry?
- Not always, but it often carries a tone of mild irritation, surprise, or casual curiosity. In friendly conversation, it can be neutral, but if you want to be polite or avoid sounding confrontational, use 为什么.