为什么

为什么 (wèi shénme) is the standard Chinese question word for 'why' — literally 'for what (reason).' It works in spoken and written Chinese and covers both 'what is the cause' (你为什么迟到？why are you late?) and 'what is the purpose' (你为什么学中文？why are you studying Chinese?). Two things differ from English: first, 为什么 stays in its natural position in the sentence — usually right before the verb — so word order does NOT invert the way it does in English ('Why are you late?'

vs 你为什么迟到？). Second, Chinese does not require a question particle like 吗 when 为什么 is present; the question word alone makes it a question. A more colloquial alternative is 怎么 (zěnme), which adds a flavor of surprise: 你怎么迟到了 ('how come you're late?').