1
- for what reason or purpose为什么：
why did he do it?
他为什么做这件事？
1.1
- with negative used to make or agree to a suggestion为什么（表示建议或同意建议）：
why don't I give you a lift?
我何不让你搭个便车呢？
1
- (with reference to a reason) on account of which; for which为什么; 所以：
the reason why flu jabs need repeating every year is that the virus changes.
需要每年打流感预防针的原因是因为病毒会变异。
1.1
- the reason for which为什么：
each has faced similar hardships, and perhaps that is why they are friends.
他们每个人都曾碰到相似的困难, 这也许就是为什么他们能成为朋友。
1
- expressing surprise or indignation唷; 哎呀; 嗨（表示惊讶、愤怒等）：
Why, that's absurd!
唷, 真是荒谬！
2
- used to add emphasis to a response呃（表示强调）：
'You think so?' 'Why, yes.'
“你真的这么想的？”“呃, 是的。”
(pl. whys)
- a reason or explanation原因; 理由：
the whys and wherefores of these procedures need to be explained to students.
这些手续的缘由都必须一一解释给学生听。
短语
why so?
- for what reason or purpose?为什么这样？
词源
Old English hwī, hwý 'by what cause'， instrumental case of hw æt 'what'， of Germanic origin.