when既指时间点，也可指一段时间，while只指一段时间。when从句的动作和主句的动作既可以同时也可以先后发生，while从句的动作和主句的动作必须同时发生。when引导的时间状语从句为一般过去时，while引导的时间状语从句为过去进行时。
1、when例句
When are you going home?
你什么时候回家?
When eating a whole cooked fish, you should never turn it over to get at the flesh on the other side.
吃一整条鱼时，切忌把它翻过来去吃另一面的肉。
When I met the Gills, I had been gardening for nearly ten years.
遇到吉尔一家时我已经做了近10年的园艺工作。
When he brought Imelda her drink she gave him a genuine, sweet smile of thanks.
当他把饮料拿给艾梅尔达时，她真诚而甜美地向他微笑以示感谢。
I asked him when he'd be back to pick me up.
我问他什么时候回来接我。
2、while例句
They were grinning and watching while one man laughed and poured beer over the head of another.
当一个男人大笑着把啤酒倒在另一个人头上时，他们都在乐呵呵地看着。
The two ministers have yet to meet, but may do so while in New York.
两位部长尚未会面，但可能会在纽约碰头。
Marianne was tempted to turn the large rooms into traditional French-style salons, while Howard was in favour of a typically English look.
玛丽安娜想把这些大房间弄成传统法式客厅的样子，但是霍华德喜欢典型的英式风格。
While the numbers of such developments are relatively small, the potential market is large.
尽管这种增长的数量相对较小，但是潜在的市场是巨大的。
They walked on in silence for a while.
他们继续默默无语地走了一会儿。
