是連詞。
adv.(副詞)
For what purpose， reason， or cause with what intention， justification， or motive:
Why is the door shut? Why do birds sing?
門爲什麼關了?鳥爲什麼唱歌?
conj.(連接詞)
The reason， cause， or purpose for which:
爲…的原因、起因或目的:
I know why you left.
我知道你離開的原因
Usage Problem On account of which for which:
【用法疑難】 因爲，爲什麼:
"The reason why [regular verbs] are called regular is that we can predict what all the other three forms are" (Randolph Quirk)
"[規則動詞] 之所以稱爲規則是因爲我們能夠預知動詞另三種形式的變化" (倫道夫·夸克)
n.(名詞)
【複數】 whys
The cause or intention underlying a given action or situation:
原因，動機:在一特點行爲或情況下隱藏的起因或目的:
studying the whys of antisocial behavior.
研究反社會行爲的原因
A difficult problem or question.
難題，令人費解的問題
interj.(感嘆詞)
Used to express mild surprise， indignation， or impatience.
用於表示輕微的吃驚、生氣或不耐煩
