高中英语情态动词和形容词比较级讲义.docx

情态动词一、 情态动词的基本用法1. 表示必须、一定。must表示主观上的必须，而have to 表示职责或义务，强调客观。In crowed places like airport and railway stations, you must take care of your luggage.There was no bus, so we had to go to school on foot.2. 表示推测或可能性A. must表示推测仅用在肯定句中，must用于否定句时，表示禁止；can 或could也可以表示推测, 其中cant表示“不可能”；对过去的行为动作或状态的推测用must/may/might/cant/couldnt+ have doneShe is wearing a long face. She must be angry.That cant be my dad, he is now abroad.B. may 或might 用于肯定句，might可能性较小，否定句可译作“可能不”。You might just as well tell the manufacturer that the male customers may not like the design of the furniture.C. Should/ought to 表示推测时，是指有一定依据的推测、推论或可能性，意为：可能、应该。You should /ought to pass her chemistry final.3. 表示请求或许可A. may 用于疑问句中表示询问许可，May I 答句是Yes, you may.否定句用No, you mustnt.还可以用can, could, might等表示许可。May I use your eraser?Yes, you may. /No, you mustnt.B. can表示许可时基本同may.You can use my mobile phone on condition that you promise not to lend it to others.C. shall 用于第三人称可以表示向第二人称询问是否允许第三人称做某事。Secretary: Shall he come in?Manager: Let him in please.4. 表示必要need 作为情态动词用于疑问句或否定句，Need you?的肯定句答语是：Yes, I must.否定句的答语是：No, I neednt/dont have to.对问句Must?表示有必要做某事的肯定答语是：Yes, you must./you have to.否定句的答语是：No, you neednt/dont have to/dont need to.You neednt come if you are busy.You must finish the project by Friday.5. 表示能够A. 表示现在的或一般的能力用can 或be able to, can比be able to 更普遍，be able to do 表示经过努力所具有的能力，有较多的时态变化。A left-luggage office is a place where bags can be left for a short time, especially at a railway station.Are you able to type?B. 如果表示在过去某一待定的时刻经过努力终于做成了某事，用was/were able to do sth.相当于managed to do sth或succeed in doing sth, 如果没有做成则可以用couldnt 或wasnt/werent able to do.I was able to make her believe me.6. 表示建议或征求意见A. shall 用于第一、三人称表征求意见或建议。Shall we meet at the school gate tomorrow morning.B. will 的疑问句表请求邀请Will you lend me your eraser?C. would 表示愿望、意愿、建议或看法。a. 表示强烈的愿望和意愿“I would do anything for the soldiers.” said the boy.b. 表示请求语气时比will 委婉，并不表示过去意义。wouldnt 表示请求、邀请，没有否定的意思。Wouldnt you take a seat? 请坐。c. would表示意愿，用在一些固定短语中，如：would like/would love to do sth; would rather do sth.I would like to have gone to the cinema, but I had an unexpected visitor that evening.D. had better 表示建议，意为：最好强调现在或将来。Youd better come early.E. Could/might/would表示委婉的请求，肯定答语分别是can/may/will.Could I sit here?Of course, you can.7. 表示敢dare作为情态动词时表示敢，用于疑问句或否定句；作为行为动词时同其他动词一样用于各种句式，跟动词不定式作宾语，在疑问句和否定句中可以省略to, I dare say是一个固定短语，意为“我认为、我相信”。Tom darent go out alone when it is dark. (情态动词)Tom doesnt dare (to) go out alone when it is dark. (行为动词)8. 表示应该should 表示义务、责任、命令、劝告，意为应该，ought to 表示义务、约束力、同should ,但是语气比should强，比must 弱，must意为应当做。I should pay Tracy a visit, but Im not sure whether I will have time this Sunday.Humans ought to stop polluting nature.You must take the cost into consideration.9. 表示命令、警告、威胁A. shall 与第二、三人称连用表示命令、许诺、警告、威胁等，表示说话人强烈的意志.You shall get an answer from me by tomorrow.B. mustnt是must 的否定形式，表示禁止，是一种命令、威胁或警告。Tom, you mustnt leave all your clothes on the floor like this!10. 表示惊讶、难以置信A. should 用于疑问句中可以表示惊讶、难以置信的事情Why should he tell a lie?B. can用于疑问句或否定句可以表示惊讶、不相信等感情色彩。How can you say that you really understand the whole story if you have covered only part of the article?11. 表示宁愿would rather意为宁愿，后跟动词原形，同used to, had better一样也被看作是情态动词，有时称半情态动词。She would rather work in the countryside.12. 表示偏偏must可以表示偏偏，偏要，指不愉快的事。After I gave her my advice, she must go and do the opposite.二、情态动词+不定式完成时 1. must have done 表示对过去的事情肯定推测，意为：一定做过某事，只能用于肯定句。 It must have rained last night, for the road is all wet. 2. cant/couldnt have done 都可使用在疑问句和否定句中表示推测，可看做must表推测对应的否定形式，cant 比couldnt的语气强，强调从现在角度出发推测过去某事的不可能性, 但当主句的谓语动词为过去式时，表示假定或推断的从句必须用couldnt have done. We knew he couldnt have crossed the river, because the bridge was broken and there was no boat. 3. could have done 表示过去有能力或有可能做某事，而因某种原因未做，有惋惜、遗憾、批评、责备的含义。 He could have passed the exam, but he was too careless. 4. should have done 表示本该做某事，而实际上没做，shouldnt have done 表示本来不应该做某事，而实际做了。含有指责对方或自责的意味。 I told your friend how to get to the hotel, but perhaps I should have driven her there.5. may/might have done 用于对过去的事情进行推测，表明说话人对过去可能发生的行为或存在的状态的一种怀疑，might表达的可能性比may要小得多。如果主句的谓语动词是过去时，从句必须用might have done.表某事本来可能发生，而实际上未发生也只能用might have done. You might have read about it in the papers.6. need have done 表示本来需要做某事而没有做，neednt have done 则表示本来不需要做某事而做了。I neednt have taken the umbrella, for the weather is fine.7. darent have done 用在否定句中表示过去本来不敢做某事，但是现在敢做了。 I darent have done it yesterday, but I think I dare now.8. was/were would like to have done 表示本来打算做某事但是却干了别的事。 I would like to have gone to the party last night but I had to work extra hours to finish a report.9. would have done 虚拟语气，表示对过去事情的假设，意为：本来会做。 I would have told you all about the boys story, but you didnt ask me.形容词和副词的比较等级1. 同级比较A. 双方比较程度相同的时候，用as+形容词或副词的原级+as 这一结构。I think physics is as important as maths.B. 双方比较程度不同等时，用 not+as/so +形容词或副词的原级+as这一结构。It is not as/so warm today as yesterday.C. 当同级比较的形容词与单数可数名词连用时，应注意不定冠词的位置，通常为：as+形容词+a/an+单数名词+as 这一结构。Would you like to join us?Sorry, Im not so good a player as any of you.2. 比较级A比较双方中一方超过另一方的时候，要用 形容词/副词的比较级+than+比较对象 这一结构。 Zhang Hua is taller than Wang Ping.B. 表示不如用less+原级+than 这一结构。 The film is less interesting than that one.C. 除比较句中与than连用表示比较之外，下面的词语后面必须用to构成比较，常用的词有inferior, superior, junior, senior, prior. He is superior to Mr. Wang in English.D. 表示两个人/物之间比较的，用the +比较级+n+of+the+名词/代词 这一结构。 She is the taller of the two girls.E. 表示越来越用 形容词比较级+and+ 形容词的比较级； the+形容词/副词比较级，the +形容词/副词比较级。 It turned warmer and warmer. The harder he works, the more progress he has made.F. 表示几倍于时，用倍数+asas或倍数+比较级+thanOur classroom is three times larger than yours.G. 形容词比较等级前可以用much, very much, even, still, far等来修饰，表示比较的程度。 Toms handwriting is far better than Johns. H. 其他含有比较级的短语和句式 morethan与其说倒不如 more or less 几乎、大约 more than 多于 less than 少于 sooner or later 迟早、早晚 whats more 而且 no sooner than 一就 not more than=at most 至多，不超过 no more than=only 仅仅、只不过 no less than =as many as 有之多 not less than =not fewer th