Definitions
1.nounReason"A good article will cover the who, the what, the when, the where, the why and the how."
2.adverbFor what cause, reason, or purpose (interrogative adverb).
3.adverbFor which cause, reason, or purpose (relative adverb)."That's the reason why I did that."
4.interjectionAn exclamation used to express indignation, mild surprise, or impatience.