Meaning of why in English
Interrogative adverb
1. used to ask about the reason for something; on what grounds
Why are you late?
2. ｟- don’t you do?, – not do?｠ used to make a suggestion
Why not ask her to go with you?
3. ｟- not?｠ used to express agreement
"Can I borrow your computer?" "Sure[Yes], why not?"
1. on account of which; for which
The reason why she came so lately is not evident.
2. the reason or purpose why; the reason or purpose for which
I don't know (the reason) why he's angry.