WHY, adverb [Latin , for what. The original phrase is for what, for why ]
1. For what cause or reason, interrogatively.
Turn ye, turn ye, for why will ye die? Jeremiah 27:13.
2. For which reason or cause, relatively.
No ground of enmity, why he should mean me ill.
3. For what reason or cause; for which; relatively.
Turn the discourse; I have a reason why I would not have you speak so tenderly.
4. It is used sometimes emphatically, or rather as a expletive.
If her chill heart I cannot move, why Ill enjoy the very love.