while引导状语从句,有以下两种含义：
1．表示某个动作正在进行的同时,另一动作也在进行之中,这时主从句都用进行时态,有对同类的两个动作进行对比的意味.如：
While I was playing the piano,she was dancing．我在弹钢琴,她在跳舞.
While Jim is picking apples,Kate is carrying apples to the truck．吉姆正在摘苹果,凯特正在把苹果搬到卡车上去.
2．表示某个动作正在进行时,又发生了另一动作（该动作用一般过去时）.如：
While I was reading,I fell asleep．我读着读着就睡着了.
While we were swimming in the river,we saw a fish jump out of the water．我们正在河中游泳时,看见一条鱼跃出了水面.
〔相关链接〕
while还有以下几种常见用法：
1．只要（＝as long as）
There will be life while there is water and air．只要有空气和水,就会有生命.
2．而；然而〔表示对比〕
He is a driver while I'm a teacher．他是司机,而我是老师.
3．虽然（＝although）；尽管〔表示让步〕
While I see what you say,I can't agree with you．虽然我能理解你说的话,但是我不能同意你.
4．用作名词,表示“一会儿或一段时间”,常与a,the或this等连用.如：
Just wait a while and then I will help you．等一下,我会来帮你的.
Where have you been all this while?这一阵子你一直都在哪儿?