when

adv.

1. 什么时候；何时；什么情况下；什么场合下
   at what time; on what occasion
   1. When did you last see him?
      你上次什么时候见到他的？
   2. When can I see you?
      我什么时候可以见你？
   3. 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’
   1. Sunday is the only day when I can relax.
      星期日是我唯一可以休息的日子。
   2. 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
   1. 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。

pron.

1. 什么时候；何时
   what/which time
   1. Until when can you stay?
      你可以待到什么时候？
   2. ‘I've got a new job.’ ‘Since when?’
      “我有了份新工作。”“什么时候开始的？”

conj.

1. 在…时候；当…时；在…期间
   at or during the time that
   1. I loved history when I was at school.
      我上学时喜欢历史。
2. 在…之后
   after
   1. Call me when you've finished.
      你完成后就打电话给我。
3. 在任何…时候
   at any time that; whenever
   1. Can you spare five minutes when it's convenient?
      方便时能占用你五分钟时间吗？
4. 一…就；刚…就
   just after which
   1. He had just drifted off to sleep when the phone rang.
      他刚睡着电话铃就响了。
5. 考虑到；既然
   considering that
   1. How can they expect to learn anything when they never listen?
      既然他们从不听讲，他们怎么能指望学到东西呢？
6. 虽然；然而；可是
   although
   1. She claimed to be 18, when I know she's only 16.
      她自称是18岁，可是我知道她才16。

1. QUEST (用于疑问句)什么时候，何时
   You use when to ask questions about the time at which things happen.
   1. When are you going home?...
      你什么时候回家？
   2. When did you get married?...
      你什么时候结的婚？
   3. When is the press conference?...
      记者招待会何时举行？
   4. When were you in this house last?...
      你最后一次在这房子里是什么时候？
   5. 'I'll be there this afternoon.' — 'When?'
      “我今天下午会去那里。”——“什么时间？”
2. CONJ-SUBORD (表示两事同时发生)在…时，当…时
   If something happens when something else is happening, the two things are happening at the same time.
   1. 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。
   2. Mustard is grown in the field when weeds are there, rather than when the growing crops are there.
      芥菜要在地里长杂草而不是长庄稼时种植。
3. CONJ-SUBORD (引导从句，表示某事发生于另一活动、事件或情形期间)在…的过程中
   You use when to introduce a clause in which you mention something which happens at some point during an activity, event, or situation.
   1. 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。
4. CONJ-SUBORD (引导从句，说明主句动作已经发生或将要发生时的情况)其时
   You use when to introduce a clause where you mention the circumstances under which the event in the main clause happened or will happen.
   1. 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。
   2. I'll start to think about it when I have to write my report.
      我要写报告时会对此予以考虑的。
5. CONJ-SUBORD (尤用于动词和形容词后引导从句，表示某事发生的时间)什么时候,何时
   You use when after certain words, especially verbs and adjectives, to introduce a clause where you mention the time at which something happens.
   1. I asked him when he'd be back to pick me up...
      我问他什么时候回来接我。
   2. I don't know when the decision was made...
      我不知道决定是什么时候作出的。
   3. It is important to check when the laboratory can do the tests.
      核实一下实验室何时可以进行这些测试是很重要的。
6. PRON-REL (用于引导从句，限定或指示某事发生的时间)…的时候
   You use when to introduce a clause which specifies or refers to the time at which something happens.
   1. He could remember a time when he had worked like that himself...
      他还能记得自己一度工作起来也是那个样子。
   2. She remembered clearly that day when she'd gone exploring the rockpools...
      她清楚地记得她去岩石区潮水潭探险的那天。
   3. In 1973, when he lived in Rome, his sixteen-year-old son was kidnapped.
      1973年他在罗马居住时，他16岁的儿子遭到了绑架。
7. CONJ-SUBORD (用于引出某个观点、评论或问题的原因)既然，考虑到
   You use when to introduce the reason for an opinion, comment, or question.
   1. How can I love myself when I look like this?...
      我这个样子，怎么能对自己满意呢？
   2. Emerald starlings are fairly small when compared with other such birds.
      与同类的其他鸟相比，翠辉椋鸟要小很多。
8. CONJ-SUBORD (用于引出使句子的其他部分显得让人吃惊或不大可能的事实或评论)虽然，然而,可是
   You use when in order to introduce a fact or comment which makes the other part of the sentence rather surprising or unlikely.
   1. Our mothers sat us down to read and paint, when all we really wanted to do was to make a mess...
      我们的母亲让我们坐下来读书和画画，而我们真正想做的却是打打闹闹。
   2. The temperature sensor is making the computer think the engine is cold when, in fact, it's hot.
      温度传感器发给计算机的信息为发动机是冷却的，可实际上它的温度很高。

1. When he returned, she and Simon had already gone
   他回来时，她和西蒙已经走了。
2. I knew him when he was a little boy
   他还是个小男孩的时候我就认识他了。
3. The driver lost control when a tyre burst
   一个车胎爆了，司机失去了控制。
4. I was a little surprised when she consented.
   我有点儿吃惊她竟然同意了。
5. It's a terrible thing when nobody wants to dance with you
   没有人想和你跳舞是一件很糟糕的事情。
6. He's going to fix a time when I can see him
   他会确定一个我和他会面的时间。
7. When you have got a handle on your anxiety you can begin to control it.
   一旦了解了自己焦虑的原因，你就开始能控制它了。
8. I lost my job when the company moved to another state
   公司搬到了另一个州，我便失业了。
9. I parried, and that's when my sword broke.
   我挡了一下，把我的剑挡断了。
10. When are you going home?
    你什么时候回家？
11. When did you get married?
    你什么时候结的婚？
12. When is the press conference?
    记者招待会何时举行？
13. When were you in this house last?
    你最后一次在这房子里是什么时候？
14. 'I'll be there this afternoon.' — 'When?'
    “我今天下午会去那里。”——“什么时间？”
15. 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。
16. Mustard is grown in the field when weeds are there, rather than when the growing crops are there.
    芥菜要在地里长杂草而不是长庄稼时种植。
17. 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。
18. 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。
19. I'll start to think about it when I have to write my report.
    我要写报告时会对此予以考虑的。
20. I asked him when he'd be back to pick me up
    我问他什么时候回来接我。
21. I don't know when the decision was made
    我不知道决定是什么时候作出的。
22. It is important to check when the laboratory can do the tests.
    核实一下实验室何时可以进行这些测试是很重要的。
23. He could remember a time when he had worked like that himself
    他还能记得自己一度工作起来也是那个样子。
24. She remembered clearly that day when she'd gone exploring the rockpools
    她清楚地记得她去岩石区潮水潭探险的那天。
25. In 1973, when he lived in Rome, his sixteen-year-old son was kidnapped.
    1973年他在罗马居住时，他16岁的儿子遭到了绑架。
26. How can I love myself when I look like this?
    我这个样子，怎么能对自己满意呢？
27. Emerald starlings are fairly small when compared with other such birds.
    与同类的其他鸟相比，翠辉椋鸟要小很多。
28. Our mothers sat us down to read and paint, when all we really wanted to do was to make a mess
    我们的母亲让我们坐下来读书和画画，而我们真正想做的却是打打闹闹。
29. The temperature sensor is making the computer think the engine is cold when, in fact, it's hot.
    温度传感器发给计算机的信息为发动机是冷却的，可实际上它的温度很高。

  when as while【导航词义：当…时】

  when conj. 在…时，当…时

〔辨析〕所引导的状语从句中，谓语可以是延续性动词，也可以是瞬时动词，其动作既可以和主句的动作同时发生，也可以在主句的动作之前或之后发生。

  as conj. 当…时，（正当）…的时候

〔辨析〕引导状语从句时，侧重指从句中的动作与主句中的动作同时发生或同时进行，一般持续时间不长，其谓语可以是延续性动词，也可以是瞬时动词。

  while conj. 当…时，在…期间

〔辨析〕指在某事发生之际或发生的过程中，另一事又发生。所引导的状语从句中，谓语应为延续性动词，而不用瞬时动词，强调其动作与主句中的动作同时发生，但持续时间一般较长；有时也可指主句的动作在从句的动作过程中发生。

conj.

as and when

• （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。