a. while引导的动作必须是持续性的,强调某一段时间内,主句和从句动作同时发生,相当于during the time that...。如：
    Strike while the iron is hot.趁热打铁。
    Please don't talk so loud while others are working.别人在工作时,请不要高声谈话。
    b. while除了可用作从属连词之外,还可用作并列连词,表示相对关系“然而”。如：
    I like watching TV while he likes reading.我喜欢看电视,而他喜欢读书。
    She thought I was talking about her daughter,while,in fact,I was talking about my daughter.
    她以为我在谈论她的女儿,而事实上我是在谈论我的女儿。
    c. while引导让步状语从句,相当于although,但一般位于主句之前。如：
    While I understand your point of view I don't share it.
    我虽然了解你的观点,但不敢苟同。
    d. while引导条件状语从句,相当于as/so long as,翻译成“只要”。如：
    While there is life,there's hope.只要有生命,就有希望。