why · adverb /wɑɪ/
why (ASK ABOUT REASON)
A1 used to ask about the reason for something
Dictionary examples:
"I'm going home." "Why?"
Why did you choose to live in Phoenix?
Why wait? Let's leave now.
Learner example:
Why couldn't you come? (Key English Test; A2; Chinese)
why (TALK ABOUT REASON)
B1 used to talk about the reason for something
Dictionary examples:
I don't know why she isn't here.
Exactly why he died is a mystery.
There is no reason why we shouldn't succeed.
Learner example:
Also, you didn't say why the photography and painting courses were so popular. (First Certificate in English; B2; Greek)
why don't you?/ why not do sth?
A2 used to make a suggestion
Dictionary examples:
Why don't you come with us?
Why not give it a try?
Learner example:
Why don't we play tennis? (Key English Test; A2; French)
why not?
B1 used to agree with something that someone has suggested
Dictionary example:
"Let's get some ice cream." "Sure, why not?"
Learner example:
She said, I have two tickets for a new film [with] Tom Cruise - would you like to come with me? Well I said why not, so I went with her to see this film. (Preliminary English Test; B1; Italian)
