since,before,when,after等的区别

1、高考英语常考句式it is +时间+ since (before, when)请注意以下三个句式的区别和意思上的差异（其中的is根据情况可以有其他时态形式）：It is +时间段 + since的意思是“自从 以来有一段时间了”。It is +时间点 + when的意思是“当 的时候时间是 ”。It is +时间段 + before的意思是“在 之前有一段时间”。请看以下用例：It s ten years since they got married.他们结婚到现在已经十年了。It was past one oclock when he came in.他回来时已经一点多了。It won t

2、be long before they understand each other.过不了多久他们就会互相了解的。有时翻译可以比较灵活：It s a long time since I met you last.好久不见了。( 直译：自上次见到你以来有很长一段时间了。 )It s about three years since I last played basketball.译：自从我上次打篮球以来已差不多有三年了。)我差不多有三年没有打篮球了。( 直请看有关高考题( 答案为DDBCDC)：1.That was really a splendid evening. It s years _

3、I enjoyed myself so much.(安徽卷 )beforeA.whenB.thatD.sinceC.ince2.A.It was some time _we realized the truth. (whenB.untilD.before山东卷)C.s3. Did Jack come back early last night?Yes. It was not yet eight o A. beforeclock _he arrived home. (B.whenD.until福建卷 )C.that4.Scientistssay it may be fiveorsix years

4、_it is possible totest thismedicineon human patients. (福建卷 )A.sinceB.afterC.beforeD.when5.It was eveningwe reached the little town of Winchester. (天津卷 )A.thatB. untilC. sinceD. before6.It _ long before we _ the result of the experiment. (上海春 )A.will not be; will knowB.is; will knowC.will not be; kno

5、wD.is; know【全真模拟训练】1. It was about midnight _ we found the lost child, crying under a tree.A.thatB.untilC.whenD.where2. Its some time _ I have spoken to you about this matter.A.thatB.unlessC.sinceD.until3.It was ten _ he stood at aunts door and rang the bell.A.whenB.untilC.sinceD.that4. I think it w

6、on t be long _ they understand each other.A.whenB.untilC.sinceD.before5. How pleased I am tonight! ItA. whens years _ we had so great a time together.B.thatC.beforeD.since6. It was some time _ we realized how important the matter is.A.whenB.untilC.sinceD.before7. Did you come home very late last nig

7、ht?No. It was just half past seven _ I appeared before my parents.A.thatB.whenC.untilD.since8. How time files! It seems like years _ I last saw you.nceA.whenB.thatD.beforeC.si9.A.It s more than half whena century_ the People s RepublicB.thatof China was liberated.C.sinceD.after答案： 1 5 CCADD6 9 DBCCw

8、hen引导时间状语从句具体地说，它有以下几种含义：1表明一个动作发生的时候，另一个动作正在进行之中。例如：When the teacher came into the classroom，we were reading English当老师走进教室时，我们正在读英语。2表明当某一动作正在进行时，另一动作发生了。如：When Kate was flying a kite，she found a wallet lying on the ground凯特正在放风筝时，她发现地上有个钱包。特别提示当when 从句放在主句之后时，它更强调某一动作的突然性，此时的when 相当于 and thenand

9、suddenly ，just at that time。如；1We were watching TV when the telephone rang（ We were watching TV and suddenly the telephone，rang ）我们正在看电视，（突然）电话铃响了。试比较： When we were watching TV， the telephone rang我们正在看电视时，电话铃响了。2The boys were playing football when it began to rain男孩子们正在踢球时，（不料）开始下雨了。3 I was taking a

10、 walk when I came across Lily我正在散步时，（没想到）遇见了莉莉。特别是主句中有just ，或 when 从句中有 suddenly 时，这种突然性更为明显、强烈。Until直到 .为止 , notuntil直到才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。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 Let ”s get in the wheat before t

11、he sun sets.）否定句：She didn ” t arrive until 6 o” clock.她直到 6 点才到。否定句可用另外两种句式表示。(1)Not until在 句首，主句用倒装。Not until the early years of the 19th century did man know what heat is.直到 19 世纪初，人类才知道热能是什么。Not until I began to work did I realize how much time I had wasted.直到我开始工作，我才认识到了我已蹉跎了几多岁月。(2) It is not u

12、ntil这that是一 个强调结构。如本题。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。It will be four days before they come back.他们要过四天才能回来。Einstein almost knocked me down before he saw me.爱因斯坦几乎把我撞倒才看到我。before 作为连词的用法其基本含义是 “

13、在之前 ”，又可以根据不同语境灵活翻译成“才 ”、 “还没来得及就 ”、“趁 ”、“就”等。具体用法如下：) 与情态动词can/could连用这时候从句虽为肯定形式，根据汉语表达习惯译成“还没来得及就 ”， 目的在于强调从句动作发生之前，主句动作已发生。如： Before I could get in a word，he had measuredme. 我还没来得及插话他就为我量好了尺寸。Before she could move，she heard a loud noise，whichgrew to a terribl eroar她还没来得及迈步，就听见一声巨响，接着就是可怕的隆隆轰鸣。)

14、用于肯定句中强调主句所表达的时间，距离长，或花费的精力大， 译成 “才” We had sailed four days andfour nights before we saw lands.我们航行了四天四夜才看到陆地。We waited a long time beforethe train arrived.我们等了很长时间火车才到。) 用于否定句中，强调主句所表达的时间，距离短，或花费的精力小，译成“不到就”如： We hadntrun a mile before he felt tired.我们跑了还不到一英里他就累了。) 主句含有 hardly ，scarcely 等半否定副词时可以

15、译为“刚就”这时候主句应用过去完成时态，从句用过去时，还可以用 when 替代 before 如： We had scarcely reached the school before/when the bellrang.我们刚到学校铃声就响了。) 有时还有 “宁愿 ”的意思I d shoot myself before I apologized to him.我宁死也不向他道歉。) 用于 It+be/take+ 时间段 +before 句型在这一句型中又可以根据主从句的时态分成两种情况。若主句是一般时将来时态，从句是一般现在时.若主句是肯定句意思是“要过多长时间才”；若主句是否定形式翻译成 “

16、用不了多久就 ”。 It will be two weeks before everything returns to normal.两周之后一切才能恢复正常。It will be many years before the situation improves.这种状况或许要过许多年才能得以改善。It won t be long before we meet again. 用不了多久我们就会再见面的。这时若主句是一般过去时从句也是一般过去时。若主句是肯定句翻译成“多长时间之后才”，若主句是否定形式翻译成“没过多久就 ”。如： It was some time before I realize

17、d the truth.过了很长一段时间我才了解到真相。It wasn tlong before she became a brave solider.没过多久她就成了一名勇敢的战士。After that it still tookseven years before they got married.他们又过了七年才结婚。注意：当主句的谓语动词为延续性动词时， before 与 until 有时可以互换。 It was an hour before/until the police arrived.) 和其它相似句型的区别有时候 before 引导的时间状语从句与since ， when 引

18、导的时间状语从句在下列结构中较相似，容易混淆。“It be +时间段+ since 引导的时间状语从句”表示 “自从已经有多长时间了 ”。主句用一般现在时或现在完成时。如：It s two years since we arrived here.我们到这两年了。“It be +时间点+when 引导的时间状语从句”表示 “某个动作发生时，是某个时间”。主句谓语动词可以是一般过去时，也可以是一般将来时。如：It s Dec 18 when I was born.我出生于 12 月 18号。) before long和 long before的区别before long意为 “不久，很快 ”（其中

19、 before 是介词， long 是名词），常在句中作状语，多与动词的过去时或将来时连用。例如：The work will be finished before long.工作不久就会完成。long before意为 “很久以前 ”（其中 long 是副词。 long before单独使用时， before是介词； long before后接从句时， before 是连词。）这个词组常与过去时或过去完成时连用，跟从句时也可用在一般现在时的句子中。例如：She said that she had heard of it long before.她说她早就听说过此事。It will be lon

20、g before he arrives.还要等很久他才能到达。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。After 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正好与before 引导的从句相反。练习 (2004 天津 )It was evening _ we reached the little town of Winchester.A . th

21、at B.until C.since D.when2.(2004 全国 )Several weeks had gone by _ we realized the painting was missing.A.as B.before C.since D.when3.(2005 广东 )The America Civil War lasted four years _ the North won in the end.A.after B.before C.when D.then4.(2005 山东 )It was some time _ we realized the truth.A.when B

22、.until C.since D.before5.(2006 四川 )-Why didn t you tell him about the meeting？ -He rushed out of the classroom _ Icould say a word.A.before B.until C.when D.after6.(2006 福建 )-How long do you think it will be _ china sends a manned spaceship to the moon？-Perhaps two or three years.A.when B.until C.th

23、at D.before参考答案： DBBDADsince一、若主句的谓语动词是现在时态，从句的谓语动词是非持续性动词，则从句的动词只能用一般过去式：IIt is(or has been)two months since he fell ill (不能用 has or hadfallen i11)( 自)他生病 ( 以来 )已有两个月了。2 It has been(or is)about ten minutes since the film began (不能用 hasor had begun)( 自 )电影开演 (到现在 ) 大约已有 10 分钟了。二、若主句和从句的谓语动词都是过去时态，从句

24、的谓语动词又是非持续性动词，主句和从句的谓语动词时态搭配则有四种情况：IIt was two months since he fell ill( 自)他生病 (以后 )到那时已有两 个月了。 (以下三句的译文跟该句相同)2It had been two months since he had fallen i113 It had been two months since he fell i114 It was two months since he had fallen ill三、若主句的谓语动词是现在时态，从句的谓语动词是持续性动词的过去时形式， since 从句表示的时间应从该从句动词的

25、终点算起：IIt is(or has been)two months since he was ill(was ill=got well)(自 )他病愈 ( 以来 )已有两个月了。2 It is(or has been)two months since he lived here (1ived here=movedaway)( 自) 他搬走 ( 至今 )已有两个月了。四、若主句的谓语动词为现在时态，从句的谓语动词是持续性动词的现在完成时形式，则since 从句所表示的时问，要从该持续动词的起点算起：1.Its(or has been)two months since he has beenil

26、lhas been ill=fellill)( 自)他生病 (以来 )已有两个月了。2 Its(or has been)two months since he has lived here(has livedhere=moved here)(自)他搬到这儿居住(以来 )已有两个月了。五、若主句的谓语动词是过去时态，从句的谓语动词用持续性动词的过去式跟用其过去完成时形式意义相反：IIt had been(or was)two months since he had lived here（ had livedhere=moved here)(自)他搬来居住 (到那时 ) 已有两个月了。2 It h

27、ad been(or was)two months since he lived here (1ived here=movedaway)( 自) 他搬走 ( 那时 )已有两个月了。（1）when. 当 的时候，when 从句谓语动词可为延续性动词或非延续性动词。Eg. I was listening to MP3 when my friend arrived. Eg. When I was young, I would go hunting with my father in the forest. when 可作并列连词，连接两分句，意为“就在/ 刚好那时”。Eg. Jim was on h

28、oliday with his mother in a wildlife park when a poisonous snake bit him.(2)while. 在 的时候。注意while 从句须用延续性动词。Eg. While I was sweeping the floor, Mr. Zhou walked in. eg. _she left her hometown, it was snowing hard.A. WhenB. whileC. afterwhile 可作并列连词，表示比较或对比。意为“而/ 却/ 可是”eg. Mother often takes a bus to w

29、ork_Father usually goes by car.Eg. We Chinese like using chopsticks_westerners prefer knives and forks.A.whenB. whileC. becauseD. since E. that(3) before. 在 之前。主句谓语动词先于从句的谓语动作之前。before还有其它的意思“还要过多少时间/ 过了多少时间才 ”eg. He covered not more than 5 miles_it began to rain heavily.Eg. Ten years had passed_he realized he hadn t learned much.Eg. It wont be long_Mother returns home.Eg. The boy was run over by the train_she could save him.A. after B. beforeC. whenD. since