为什么？
The standalone 'Why?' Reach for this when someone has just said something and you want them to explain — a one-word follow-up. It works exactly like English 'Why?' as a complete utterance: another speaker drops a fact, you reply 为什么？and the conversation pivots to the explanation. It's neutral in tone; intonation and context do the rest of the emotional work. Don't confuse it with 为什么 used inside a longer sentence — here it stands alone.
Structure
为什么？
wèishénme?
How to Think About It
为什么 literally is 'for what,' and as a standalone it's the bare hook that pulls the next sentence out of your conversation partner. Unlike English, Chinese doesn't need 'do you' or 'is that' filler — the two characters are already a complete grammatical question. Stress and follow-up framing (curious, surprised, skeptical) come from your voice and face, not extra words.
Examples
—我不去了。—为什么？
— Wǒ bù qù le. — Wèishénme?
"I'm not going anymore." "Why?"
—这家店关门了。—为什么？
— Zhè jiā diàn guānmén le. — Wèishénme?
"This shop has closed." "Why?"
—他不喜欢这个工作。—为什么？
— Tā bù xǐhuān zhège gōngzuò. — Wèishénme?
"He doesn't like this job." "Why?"
Common Mistake
Learners try to soften the question by adding 吗 ('为什么吗？'). 吗 only attaches to yes/no questions; 为什么 is already a question word, so 吗 makes it ungrammatical. The neutral softener is 呢, not 吗.
为什么吗？
为什么？ (or 为什么呢？)
Don't Confuse With
为什么 [CLAUSE]？
Embedded in a full question — '为什么这么贵？' Use the standalone form only as a reactive follow-up; use the embedded form when you're asking about something specific in the same breath.
怎么了？
'What happened?' / 'What's wrong?' — asks about a situation, not a reason. Use 怎么了 when something seems off; use 为什么 when you want the cause of a stated fact.
为何？
Same meaning, formal/literary register. Use 为什么 in speech and casual writing; 为何 appears in news headlines and essays, almost never in conversation.
Practice
Reply with one Chinese word asking the reason: —我不去了。— ___？
Show answer
为什么
Fill in the missing character: 为___么？
Show answer
什
Arrange to ask a softened 'Why?': 呢 / 为什么
Show answer
为什么呢？
Translate the short dialogue: "I don't want to." "Why?"
Show answer
—我不想。—为什么？
Write a two-line dialogue where the second line is just 为什么？
Show answer
—明天不上课。—为什么？
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode:
Related Grammar Patterns
Acquire by listening
Hear 为什么？ in real Chinese, not in a textbook.
Fluentide picks the next news episode at your level, so this pattern shows up again and again in real context. The transcript marks it, the audio drills it. Free to start, no card.