From Longman Dictionary of Contemporary Englishwhywhy1 /waɪ/ ●●● S1 W1 adverb 1 REASONused to ask or talk about the reason for something Why are you crying? Why do we have to take all these tests? ‘She wants to meet you.’ ‘Why?’ ‘I won’t be able to come into work tomorrow.’ ‘Why not?’ I have no idea why the television isn’t working. Simon loves you – that’s why he wants to be with you. He’s angry with me and I don’t know why. There’s no reason why we shouldn’t be friends.why on earth/why ever etc (=used for emphasis when you are surprised, angry etc) Why on earth didn’t you ask me to help? ‘I don’t want us to be seen together.’ ‘Why ever not?’2 used to introduce a question that shows you do not think it is necessary to do something Why worry? You can’t do anything about it. Why waste time going to the bank when you can do it all over the Internet?3 → why not?4 → why doesn’t somebody do sth?5 → why sb?6 → why oh why ...?
Examples from the CorpusWhy not• Why do you need carpet in your new store, Bill? Why not cement floors?• This year, Victorine snorted: she and Léonie would have to do it. Why not chutney?• Every other big business has to pay market wages to its workers. Why not college sports?• Q: Why not give up an Aki Berg if you can get a Nieuwendyk?• Liturgical occasions? Why not let the people know?• They also make perfect presents. Why not make a special bookmark for Thinking Day?• Why a fear of turtles? Why not the conventional witch, robbers and monsters?whywhy2 interjection old-fashioned SURPRISEDused when you are surprised or have suddenly realized something Why, look who’s here! And I thought to myself, why, I can do that.whywhy3 noun → the whys and (the) wherefores