何で
Meanings
1
why?; what for?
usually written using kana alone
Casual interrogative asking for a reason or purpose. Often used in spoken Japanese and informal writing.
Why were you late?
What did you do that for?
2
how?; by what means?
Casual interrogative asking about method or means. Less common than the 'why' sense; どうやって is often preferred for 'how'.
How did you get here?
How did you finish so quickly?
Usage patterns
- 何で〜の？casual question asking why (with sentence-final の)
Why are you suddenly crying?
- 何で〜んですかslightly more polite question asking why
Why didn't you come to the meeting?