when与连续性的或短暂性的动词连用,从句的动作与主句的动作有可能是同时发生,也可能是从句的动作发生在前,在表示两个动作同时发生时,可与WHILE互换.例如；when we were leaving,it began to rain,when引导的从句动词是leave,发生在rain之前. While译为“在……同时”,“在…期间”,谓语动词要加延续性动词.例句：please be quiet while i ’m talking to you,.从句中是进行时时态时,一般都用while) 注;when 和while都可做并列连词,此时when表示”就在此时”,while可以译为然而,但是,表转折,强调.例句:he is good at basketball,while his brother is dood at football.
