1、英语时间状语从句讲解（一）when, while和as引导时间状语从句的用法一、when的用法如果只从现象来看，when从句用的最多的是大凡过去时，而主句的时态没有限制,根据具体情况而定。1. When he was a child he was always trying out new ideas.3. Were you writing when the teacher came in?老师进来的时候，你在写信吗？4. Sorry, I was out when you called me.对不起，你打电话来的时候我出去了。when从句的重点不在动作本身发生的状态，而只是把它作为一个时间点
2、，所以when多数情况下用的是大凡过去时，则不用正在进行时。因为如果用正在进行时，它表示的就是一段时间而不是一个时间点了。根据这一点，有的文章补充说：when从句的动词大多是瞬时动词。这种说法也可以参照。实际上，when从句也可以有其它的时态，但几乎也不用进行时，因为它也只是作为一个时间参照点。例如：2. When he had finished his homework, he took a short rest.3. Why do you want a new job when you have got such a good one already?二、while的用法相比于when来说
3、，while从句的侧重点就不一样了。while从句的侧重点在于描述动作正在发生的状态，它的意思是：当while事件正在发生的时候，另一件事如何如何。所以，while从句大凡用的是正在进行时。而另一件事的状态没有硬性的要求，根据具体情况而定。例如：1. While my wife was reading the newspaper, I was watching TV.2. While Jim was mending his bike, Lin Tao came to see him.3. While they were talking, the bell rang.正在他们谈话的时候，上课铃响
4、了。从时间的角度来看，while表示的是一段时间，是一个过程。这是while的侧重点。因此，如果含有“一段时间”的含义的时候，就可以用while。6. Strike while the iron is hot.趁热打铁。这句话中，是说趁着铁是热的这段时间，赶紧打铁。如果换成when意思就变了，相当于说铁只热了一下，打一下，然后铁就冷了。这显然不符合文意。再例：I“m going to the post office.While you“re there, can you get me some stamps?三、as的用法as从句表示的也是一件事情正在发生，另一件事也正在进行当中。但与whil
5、e从句例外的是，as从句用的大凡不用正在进行时，而只是大凡过去时。as从句大凡可以翻译成“边边”。例如：1. As my mother sang those old songs, tears ran down her cheeks.2. The students took notes as they listened.学生们边听课边做笔记。3. As we talked on, he got more and more excited.as表达的事件，往往只是主句动作发生的背景或条件时，as只是一个次要的时间说明，不像while从句有强调while动作本身的意思。因此，as常常翻译成“随着”之
6、意。例如：1. As the time went on，the weather got worse.随着时间的推移，气候更加倒霉。2. The atmosphere gets thinner and thinner as the height increases.3. As years go by，China is getting stronger and richer.少数情况下，如果强调动作正在发生，as从句也可以用正在进行时。这只能算是特例了。1. The sad mother sat on the roadside, shouting as she was crying.2. As w
7、e were going out, it began to snow.合法我们出门时，雪开始下起来。3. He came in as I was going to bed.我正要上床睡觉，他进来了。四、when, while, as的互换如果从句动作和主句动作同时发生，并且从句动作为延续性动词时，when，while，as可以互换使用。1. When /While /As we were dancing, a stranger came in.dance为延续性动词2. When /While /As she was making a phone call, I was writing a l
8、etter. make为延续五、比较while, when, as1）as, when引导短暂性动作的动词。例如：Just as / Just when / When I stopped my car, a man came up to me.2）当从句的动作发生于主句动作之前，只能用when引导这个从句，不可用as或while。例如：When you have finished your work, you may have a rest.3）从句表示“随时间推移”连词能用as，不用when或while。例如：As the day went on, the weather got worse
9、.（二）before和after引导的时间状语从句1Before是主句动作发生在从句的前面。注意before引导的从句不再用否定式的谓语，并且当before引导的从句位于主句之后，有时译成“就，才”。还要注意主句和从句之间的时间关系。当主句用将来时，从句总是用现在时；如果before引导的从句谓语用的是过去时，则主句动词多用过去完成时，这样以便体现动作发生的先后。2After表示主句动作发生在从句动作之后。主句和从句的动作的时间关系凑巧与before引导的从句相反。例如：It will be four days before they come back.他们要过四天才能回来。After we
10、 had finished the work, we went home.（从句用过去完成时，主句用大凡过去时）（三）比较until和till的用法此两个连词意义相同。肯定形式表示的意思是“做某事直至某时”，动词必须是延续性的。否定形式表达的意思是“直至某时才做某事”。动词为延续性或非延续性都可以。正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。肯定句：I slept until midnight.我一直睡到半夜时醒了。Wait till I call you.等着我叫你。（在肯定句中可用before代替。例如：Let“s get in the wheat before
11、the sun sets.）否定句：She didn“t arrive until 6 o“clock.她直到6点才到。Don“t get off the bus until it has stopped.公共汽车停稳后再下车。（四）区别：1）until可用于句首，而till通常不用于句首。例如：Until you told me, I had heard nothing of what happened.3）until when疑问句中，until要放在句首。例如：-Until when are you staying?你呆到什么时候？- Until next Monday.呆到下周一。注意
12、：否定句可用另外两种句式表示。4）Not until在句首，主句用倒装。例如：Not until the early years of the 19th century did man know what heat is.Not until I began to work did I realize how much time I had wasted.5）It is not until that.例如：It was not until I began to work that I realized how much time I had wasted.（四）巧辨before和until在日常
13、英语教学中，我们遇到学生问这样的一些问题：1.He will spend six hours at his desk_he finishes his composition.A.beforeB.untilC.afterD.when2.The bike hit the tree_I could get off.A.whenB.beforeC.whileD.until3.I knocked at the door for more than five minutes_Mrs white answered it.A.untilB.whenC.afterD.before4.It was_yesterd
14、ay_be_the secret.A.not until；that；knewB.until；when；knewC.not before；that；foundD.before；that；didn“t find怎样才能清晰地解释其选择的原因，这就涉及到until与before的区别问题。实际上，只要我们把握住两者使用时本身的含义及主句动词是终止性的，还是延续性的，肯定式，还是否定式两大点，就能简易地解决这类问题。现详细阐明如下：一、在下列情况下，两者可互换用，但含义略有例外。before表示“在之前”的意思，强调时间先后关系；而until表示“直到才”的意思，主句是肯定句则表示主句动作的终止时间；
15、主句是否定句则强调主句动作的起始时间。1.主句为否定式终止性谓语动词。多见的动词是open,start,leave,arrive,finish,stop等。例如：(1)The noise of the street didn“t stop until/before it was midnight.(2)The children won“t come back until/before it is dark.(3)I didn“t leave the lovely boy until/before his mother came home.2.主句为肯定式、延续性谓语词，这类动词用stand,s
16、tay,talk,be,wait等。例如：(1)He lived with his parents until/before he graduated from school.(2)I will wait until/before he comes to my help.(3)I shall stay heer until/before you come back.二、在下列情况下，用before不用until。1.主句这肯定式、终止性谓语动词，只用before。例：(1)He fell asleep before I could take off his clothes.(2)We arri
17、ved there before it atarted to rain.2.主句谓语动词强调动词的迟缓性，只用before，常伴有时间段状语或时间段暗示。例：(1)It was quite some time before he found the elephant at all.(2)We had walked a long way before we found some water.3.如果强调从句谓语动作未发生，就发生主句谓语动作，只用before。常译为“未及”，“不”或“不等就”。例：(1)We can leave early in the morning before it ge
18、ts too hot.(2)I must write it down before I forget it.(3)We do want to buy something now before prices go up.4.表“与其说倒不如”，“与其毋宁”只用before。例：(1)I would give up my job before I“d agree to be dismissed.(2)He will die of hunger before he will steal.5.在某些特定句型中用before。例如：(1)It was not long before the whole
19、country rose up.(2)It will probably not be long before they understand each other.三、下列情况大凡区别用until。1.主句是持续性谓语动词时，肯定、否定都可以，但意义完全例外。肯定表动作终止，而否定表动作开始。例如：(1)We discussed the problem until/before he came back.(2)We didn“t discuss the problem until he came back.2.notuntil句型尽管在某些情况下可与before互换用，但在强调句中大凡仍用un
20、til。(1)It was not until he told me that I knew it.(2)It was not until he finished his homework that he went home.综上所述，前面的4条选择题中，第1、3题强调动作发生的迟缓性应选before。第2题表动作未及发生就发生主句动作也应选before。第4题为强调句应选A项。（五）其他时间状语从句的用法1.由since引导的时间状语从句。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。大凡情况下，从句谓语动词用大凡过去时，而主句的谓语动词用现在完成时。但在It is时间
21、since从句的句型中，主句多用大凡现在时。例如：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。知识扩展1. It is since从。以来多长时间了(因为since +从句或名词，表示一段时间)It is five years since we met last time.从我们上次见面已经五年了。2. It is +before(。才)It was a long time before I went to
22、sleep again.It was an hour before(until) the police arrived.2.由as soon as, immediately, directly, instantly, the moment, the instant, the minute,等引导的时间状语从句。这些连词都表示“一就”。例如：I will go there directly I have finished my breakfast.吃完早饭，我立即到那里去。The moment I heard the news, I hastened to the spot.我一听到消息，马上赶
23、到了出事地点。As soon as I reach Canada, I will ring you up.我一到加拿大，就给你来电话。3.由by the time引导的时间状语从句。注意时态的变化：在大凡情况下，如果从句的谓语动词用大凡过去时，主句的谓语动词用过去完成时；如果主句的谓语动词用大凡现在时，主句的谓语动词用将来完成时。例如：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。注意：when while as after before as soon as since till /until by the time在时间状语从句中，要注意时态一致。大凡情况下主句是将来时的时候，从句要用大凡现在时。
