adv., int., & n.
adv. 1 a for what reason or purpose (why did you do it?; I do not know why you came). b on what grounds (why do you say that?). 2 (prec. by reason etc.) for which (the reasons why I did it).
int. expressing: 1 surprised discovery or recognition (why, it's you!). 2 impatience (why, of course I do!). 3 reflection (why, yes, I think so). 4 objection (why, what is wrong with it?).
n. (pl. whys) a reason or explanation (esp. whys and wherefores). why so? on what grounds?; for what reason or purpose?
[ OE hwi, hwy instr. of hwt WHAT f. Gmc ]