1why 
/ˈwaɪ/ adverb
/ˈwaɪ/ adverb 1 : for what reason or purpose
▪ Why did you quit your job? ▪ Why are you laughing? [=what are you laughing about?] ▪ Why is the sky blue? ▪ Why didn't you call me? ▪ Why didn't I think of that? ▪ “I can't go out tonight.” “Why not?” 2 — used to offer a suggestion or to say that a course of action is not necessary ▪ If you don't want to go, why not just say so? ▪ Instead of calling, why not e-mail instead? ▪ Why should I care about that? ▪ Why don't you come over for dinner? [=we would like to have you over for dinner] ▪ You deserve the best treatment. Why settle for less? [=you shouldn't be happy with anything less] ▪ “I'll try calling again.” “Why bother?” [=it's not worth the trouble] 3 — used to express irritation or annoyance ▪ Why can't you make up your mind? ▪ Why must I always repeat myself? ▪ Why would anyone say such a thing? ▪ Why oh why did I say something so stupid?
▪ Why did you quit your job? ▪ Why are you laughing? [=what are you laughing about?] ▪ Why is the sky blue? ▪ Why didn't you call me? ▪ Why didn't I think of that? ▪ “I can't go out tonight.” “Why not?”
