while 的用法
1 連詞 引導時間狀語從句,意為 當.時候 while 引導的句子的謂語部分必須是可以延續(xù)的動詞或結構.
My mother is cooking while my father is reading the newspaper .
She fell asleep while she was doing her homework .
2 名詞 意為 一會兒 after a while for a while
After a while,she came back .
when的用法
when 連詞 意為 當...時候 ...這時.引導時間狀語從句,與while 不同,when 引導的句子的謂語部分可以是短暫性的也可以是持續(xù)性的動詞或結構.
She fell asleep when she was doing her homework .
I was walking in the street when I saw a wallet on the ground .
I saw her singing in the room when I passed by her room .
until 的用法
1 until是連詞 引導時間狀語從句
兩個句型：.(肯定句）until....否定句）until .
They worked until it was dark .他們一直工作凌晨一點.
He didn't go until the boy's parents came back .直到那個男孩的父母回來了,他才走.
2 介詞 They kept him waiting until o'clock in the afternoon .