when：英[wen]，美[wɛn]，类似于中文的“闻”。
作为副词有以下用法：adv.
1、(used in questions 用于问句) 什么时候；何时；什么情况下；什么场合下
at what time; on what occasion
When did you last see him?
你上次什么时候见到他的？
When can I see you?
我什么时候可以见你？
When (= in what circumstances) would such a solution be possible?
什么情况下可以这么解决？
2、（用于时间的表达方式之后）在那时，其时
used after an expression of time to mean ‘at which’ or ‘on which’
Sunday is the only day when I can relax.
星期日是我唯一可以休息的日子。
There are times when I wonder why I do this job.
有时候我也不明白自己为什么要干这个工作。
3、其时；当时；当场
at which time; on which occasion
The last time I went to Scotland was in May, when the weather was beautiful.
我上次去苏格兰是在五月份，那时的天气好极了。
扩展资料：
as and when
例句：（用于在特定条件下才会发生的事情）将来…时，到时候
used to say that sth may happen at some time in the future, but only when sth else has happened
1、We'll decide on the team as and when we qualify.
将来我们具备了条件时就会决定成立这个队。
2、I'll tell you more as and when (= as soon as I can) .
我一有可能就会告诉你更多情况。
参考资料：百度百科-when
