广州初一英语Unit 8语法【精讲点拨】when引导的时间状语从句一. 概念：在复合句中，由时间连接词引导的状语从句叫做时间状语从句。
二．1.．从句动作在主句动作前发生，只用when。
When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。
When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。
2．在将来时从句中，常用when，且从句须用一般现在时代替将来时。
You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。
When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。
三．种类：1.由when, while, as引导的时间状语从句。
（1）when引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。
动作既可和主句的动作同时发生又可在主句的动作之前或之后发生，并且when有时表示“就在那时”。
When she came in, I stopped eating. 她进来时，我停止吃饭。
(瞬时动词)When I lived in the countryside, I used to carry some water for him.当我住在农村时，我常常为他担水。
（延续性的动词）（2）while强调主句的动作与从句的动作同时持续地进行，用于这一用法时while引导的时间状语从句和主句中的谓语动词必须是延续性动词，或者主句的动作发生在从句动作的进行过程中，主句中的谓语动词通常是非延续性动词，并且while有时还可以表示对比。
While my wife was reading the newspaper, I was watching TV.I met her while I was at school.I like playing football while you like playing basketball.（3）as引导时间状语从句时表示“当……时，一边……一边……”，侧重表示两个动作同时发生(包括一个主语同时进行两个动作)，或者一种动作随着另一种动作的变化而变化。
As the time went on，the weather got worse．（as表示“随着……”之意）The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。
The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。
As we was going out, it began to snow.当我们出门时，开始下雪了。
（as强调句中两个动作紧接着先后发生，而不强调开始下雪的特定时间）2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。
②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信总结：when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。
四、其他几种时间状语从句：1.由before和after引导的时间状语从句。
before引导的时间状语从句表示主句动作发生在从句动作之前。
从句不用否定的谓语形式。
从句位于主句之后时，before有时译成“才；就”。
还要注意主句和从句的时间关系。
当主句用将来时，从句总是用现在时；从句用过去时，则主句多用过去完成时，以此来体现动作发生的先后顺序。
after表示主句动作发生在从句动作之后，主句和从句的时间关系正好与before相反。
如：It will be four days before they come back.他们要过四天才能回来。
My father had left for Canada just before the letter arrived.我父亲恰好在信到达之前去加拿大了。
After we had finished the work, we went home.完成工作之后，我们回家了。
2.由till或until引导的时间状语从句。
till和until一般情况下两者可以互换，但是在强调句型中多用until。
并且要注意的是：如果主句中的谓语动词是瞬时动词时，必须用否定形式；如果主句中的谓语动词是延续性动词时，用肯定或否定形式都可以，但表达的意思不同。
till不可以用在句首，而until 可以放在句首。
I didn't go to bed until（till）my father came back.直到我父亲回来我才上床睡觉。
I worked until he came back.我工作到他回来为止。
I didn't work until he came back.他回来我这才开始工作。
3.由since引导的时间状语从句。
“自从……以来”,或“自从……以后”, since引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。
主句通常用现在完成时态，从句谓语动词用一般过去时，。
但在It is ＋时间＋since从句的句型中，主句多用一般现在时。
I have been in Beijing since you left.自从你离开以来，我一直在北京了。
It is five months since our boss was in Beijing.我们老板离开北京有五个月了。
4.由as soon as, immediately, directly, instantly, the moment, the instant, the minute, 等引导时间状语从句。
这些连词都表示“一……就”。
例如：The moment I reach Canada, I will ring you up.我一到加拿大，就给你来电话。
5.由by the time引导的时间状语从句。
注意时态的变化：在一般情况下，如果从句的谓语动词用一般过去时，主句的谓语动词用过去完成时；如果从句的谓语动词用一般现在时，主句的谓语动词用将来完成时。
By the time you came back, I had finished this book.到你回来时，我已经写完这本书了。
By the time you come here tomorrow, I will have finished this work.你明天来这儿的时候，我将已经完成此工作了。
课堂练习1. By the end of last term , I___ten books.A had finished reading B.have finish readingC.had finish to readD.finish read2.I won't believe you__ I have seen it with my own eyes.A. beforeB. untilC. afterD. when3.___ he came to study in the university, he has made much progress in the study of English.A. WhileB. WhenC. SinceD. After课后练习在下列各句的空格中填入适当的连词1．_________ he comes tomorrow, I shall ask where he has been.2．_________ he was speaking, everybody listened carefully.3．I saw her just _________ she was getting off the train.4．Have a good look at that man _________ you pass him.5．It was already eight o'clock _________ we got there.6. I was about to go out _________ a visitor came.7．We'll go to the country at the beginning of June, ______ the summer harvest will start.8. He learned to speak German _________ he was in Berlin.9. Henry is in charge of the office ________ Mr. Smith is away.10. I listen to the recorder _________ I have time.11. He had learned Chinese _________ he came to China.12. _________ the work was done, we sat down to sum up experience.13. I haven't seen him _________ he moved to the other side of the town.14. I waited ________ he came back.15. It was not ________ he took off his eyeglasses that I recognized him.16. She likes everything to be in place ________ she starts to work.17. The thieves ran away _________ they caught sight of the police.18. They decided to go back home _________ their money ran out.19. We played outside till sunset, _________ it began to rain。
