/ waɪ; NAmE / adverb , exclamation , noun
■ adverb
1.
used in questions to ask the reason for or purpose of sth :
Why were you late?
Tell me why you did it.
'I would like you to go.' ' Why me? '
( informal )
Why oh why do people keep leaving the door open?
2.
used in questions to suggest that it is not necessary to do sth :
Why get upset just because you got one bad grade?
Why bother to write? We'll see him tomorrow.
3.
used to give or talk about a reason :
That's why I left so early.
I know you did it—I just want to know why.
The reason why the injection needs repeating every year is that the virus changes.
•
IDIOMS
- why ever
- why not?
■ exclamation
( old-fashioned or NAmE ) used to express surprise, lack of patience, etc. :
Why Jane, it's you!
Why, it's easy—a child could do it!
■ noun
•
IDIOMS
- the whys and (the) wherefores
••
WORD ORIGIN
Old English hwī , hwӯ by what cause , instrumental case of hwæt what , of Germanic origin.