when基本解释
副词当时; 什么时候; （用于时间的表达方式之后）在那时; 其时
连词如果; 在…时; 既然
代词什么时候; 那时
名词时间，时候; 日期; 场合
when的近义词
when相关例句
副词
1. When did you last see Margaret?
你上一次见到玛格丽特是什么时候？
连词
1.
1. We have only three books when we need five.
虽然我们需要五本书，却只有三本。
2. We'll start when the team leader comes.
队长一来，我们就出发。
when情景对话
学校
when是什么意思
B：When is the (assignment/ project/ report) due?
什么时候交（作业/计划/报告）？
when是什么意思
A：It’s due tomorrow.
明天。
结婚纪念日
A：When is your parents’ wedding anniversary?
你父母的结婚纪念日是在哪天？
when
B：Their anniversary is in August.
他们的结婚纪念日是在八月。
旅游
A：When do we (board/ depart/ arrive)?
我们什么时候（登机（船）？/离开？/到达）？
B：At 6:49pm.
下午6点49分。
when网络解释
1. 当......时：-->是I met your sister那当时(when)的特定那一个(指明; 也是关系子句的(形容词)功能) 夜晚.
when词典解释
1. (用于疑问句)什么时候，何时
You use when to ask questions about the time at which things happen.
e.g. When are you going home?...
你什么时候回家？
e.g. When did you get married?...
你什么时候结的婚？
2. (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.
e.g. 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。
e.g. 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. (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.
e.g. 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. (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.
when的近义词
e.g. 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。
e.g. 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. (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.
when是什么意思
e.g. I asked him when he'd be back to pick me up...
我问他什么时候回来接我。
e.g. I don't know when the decision was made...
我不知道决定是什么时候作出的。
6. (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.
e.g. 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。
e.g. 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。
7. (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.
e.g. How can I love myself when I look like this?...
我这个样子，怎么能对自己满意呢？
e.g. 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. (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.
e.g. 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。
e.g. 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。