语法复习情态动词

1、 高二英语语法复习 情态动词一、区别1. 表示请求和允许: can, could , may, might. 过去式使语气更委婉，答语应用原形。 - Could I use your computer tomorrow morning?- Yes, you can.( 否定回答可用：No, Im afraid not.)2表示推测：理论可能性can主观可能性肯定句must, may ,might, （could）疑问句can/ could否定句cant/couldnt (不可能、肯定不)，may not (可能不)1)can表示理论上的可能性，指某事或情况可能发生，但并不说明实际上真的发生.

2、Children can be very tiring. 2)反意问句 He may know the plan, doesnt he? You must have studied English before, havent you? You can t have been caught in the rain last night, were you?情态动词+ do , 表示现在或将来 (+be doing)情态动词+ have done,表示过去 (+have been doing) (+have been done)3could & be able to 在肯定句中could

3、表示过去有“能力”做，was / were able to表示过去有能力而且确实做成了某一件事， 相当于managed to do或succeeded in doing sth.The fire spread through the hotel very quickly but everyone was able to get out.4. may / might(just ) as well do sth “还是好”、“不妨” You might as well tell me the truth. 你还是把真相告诉我的好。5. must和have to 1) must表示的是说话人的主观看

4、法, 而have to强调客观需要。2）否定形式含义不同。mustnt禁止，不许可，dont have to不必3) must 偏要（做令人不快的事）eg. Must you shout so loudly?6. shall和should1) 表示说话人征求对方意见和向对方请示，用于第一、三人称。 When shall my father be able to leave hospital?shall 2)表示命令、警告、允诺或威胁以及说话人的决心(文件规定)。用于二、三人称。 You shall go with me (命令) / You shall have the book when I

5、 finish it.（允诺）He shall be punished （威胁）/ Nothing shall stop me from doing it. (决心)1) 表示劝告和建议“应该”2) “按道理应当”“估计”(=ought to)They should be there by now, I think. 3） 用于第一人称表示说话人的一种谦逊、客气、委婉的语气。I should advise you not do that.我倒是劝你别这样做。should 4） 在条件句中表示“万一”，主句不一定用虚拟语气。Ask Tom to ring me up if you should

6、see him. /Should I be free tomorrow, Ill come. 5） Why / How + should 结构表示说话人对某事不能理解，感到意外、惊异等意思， 意为“竟然”，也用在某些从句中。 It seems so unfair that this should happen to me.这种事竟然发生在我身上真不公平。7. will 和would 1) 表示意志和意愿。will 指现在，would指过去。If you will listen to me, Ill give you some advice.2) 表示请求、建议，would比will委婉、客气。

7、Will (Would ) you please pass me the book?3) 表示习惯性动作，“总是”“惯于”，will指现在，would指过去。Fish will die without water. Every evening, she would sit by the window, deep in thought.4). 表示功能， 意为“能” 或“行” The machine wont work/shut /open/ lock.5) 表示预料或猜想。It would be about ten when he left home.猜想他离开家时大约点。 8. would

8、& used to1) 表示过去持续的状态和动作用used to; would不与表示状态的动词(be)连用。There used to be a hospital here. / There would be a hospital here.( ×)2) would 常与often, sometimes, for hours等表示时间的副词（短语）连用。We would sit in the yard every evening and listened to his story.3) used to 强调过去的行为同现在的对比，含有“过去怎样，而现在却不这样了”的含义.

9、eg. He will not spend the money on books as he used to.9. dare 和need两者作为情态动词都不用于肯定句，常用于否定句、疑问句和条件从句中。习惯用语 I dare say（可能，或许，我揣测）除外。实义动词用法同于一般动词。但在否定句中，dare情态动词（常用于否、疑和条件从句中）实义动词 时态 dare/dared dodare(s)/dared to do否定daren't/daredn't dodon't/doesn't/didn't (to) do 10 cannot / cant/c

10、an nevertoo /enough“越越好,再.也不过分”。注意这个句型的变体 cannotenough.如：You cannot be too careful when you drive a car.驾车时候, 越小心越好。 11 usednt 或didt use to 为used to （do） 的否定式。 Tom used not to rise at six every morning.12.比较： neednt have done & didnt need to doShe need not have come yesterday. 她昨天本不必要来的。（但却来了） S

11、he didnt need to come yesterday. 她昨天不必来。（实际上也没来）二、高频考点（情态动词+have done）情态动词现在完成式主要有两个功能：表示已经发生的情况和表示虚拟语气。1.表示对已发生情况的猜测1）must have+done, “过去一定/肯定”对已发生情况的肯定推测 否定形式为····cant / couldnt have+过去分词 即2） mustn't have+done（×）2）cant / couldnt have+过去分词, “过去一定没/肯定不/不可能”3）may / might

12、have +过去分词, “可能做了” 否定形式为···· 2.表示虚拟语气。1） neednt have + done , （本没必要做···） 表示做了不必做的事, 2）should /ought to have +过去分词，“本应该···” 过去应该做而实际并未做的动作3) should not /oughtn't tohave+过去分词, “本不应该···” 表示本不应该做某事但实际上做了4） can/could have +过去分词, “原本可以···” 表示过去本来可以做但却未做,5） would(/could/might/should have) +过去分词,“原本会···”（尤其在if引导的非真实条件句中对过去虚拟，主句中较常用）You didn't attend yesterday&