怎么 (zěn me) is a versatile question word meaning 'how' (manner) or 'why' (reason), depending on context. Unlike 什么 (shén me 'what'), which asks for a thing, or 哪 (nǎ 'which'), which asks for a choice, 怎么 asks about the way something is done or the cause. For 'why', 怎么 is more conversational than 为什么 (wèi shén me), which is the standard, clearer form.