高中英語情態(tài)動詞和形容詞比較級講義

1、情態(tài)動詞一、情態(tài)動詞的基本用法1.表示必須、一定。must表示主觀上的必須,而have to 表示職責(zé)或義務(wù),強調(diào)客觀。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.表示推測或可能性A.must表示推測僅用在肯定句中,must用于否定句時,表示禁止;can 或could也可以表示推測, 其中cant表示“不可能”;對過去的行為動作或狀態(tài)的推測用must/may/

2、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可能性較小,否定句可譯作“可能不”。You might just as well tell the manufacturer that the male customers maynot like the design of the furniture.C.Should/ought to 表示推測時,是指有一定依據(jù)的推測、推

3、論或可能性,意為:可能、應(yīng)該。You should /ought to pass her chemistry final.3.表示請求或許可A.may 用于疑問句中表示詢問許可,May I 答句是Yes, you may.否定句用No, you mustnt.還可以用can, could, might等表示許可。May I use your eraser?Yes, you may. /No, you mustnt.B.can表示許可時基本同may.You can use my mobile phone on condition that you promise not to lend itto

4、 others.C.shall 用于第三人稱可以表示向第二人稱詢問是否允許第三人稱做某事。Secretary: Shall he come in?Manager: Let him in please.4.表示必要need 作為情態(tài)動詞用于疑問句或否定句,Need you?的肯定句答語是: Yes, I must.否定句的答語是:No, I neednt/dont have to.對問句Must?表示有必要做某事的肯定答語是:Yes, you must./you have to.否定句的答語是:No, you neednt/dont have to/dont need to.You neednt

5、 come if you are busy.You must finish the project by Friday.5.表示能夠A.表示現(xiàn)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 表示經(jīng)過努力所具有的能力,有較多的時態(tài)變化。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.如果表示在過去某一待定的時刻經(jīng)過努力終于

6、做成了某事,用was/wereable to do sth.相當(dāng)于managed to do sth或succeed in doing sth, 如果沒有做成則可以用couldnt 或wasnt/werent able to do.I was able to make her believe me.6.表示建議或征求意見A.shall 用于第一、三人稱表征求意見或建議。Shall we meet at the school gate tomorrow morning.B.will 的疑問句表請求邀請Will you lend me your eraser?C.would 表示愿望、意愿、建議或

7、看法。a.表示強烈的愿望和意愿“I would do anything for the soldiers.” said the boy.b.表示請求語氣時比will 委婉,并不表示過去意義。wouldnt 表示請求、邀請,沒有否定的意思。Wouldnt you take a seat? 請坐。c.would表示意愿,用在一些固定短語中,如:would like/would love todo sth; would rather do sth.I would like to have gone to the cinema, but I had an unexpectedvisitor that

8、evening.D. had better 表示建議,意為:最好強調(diào)現(xiàn)在或?qū)怼oud better come early.E. Could/might/would表示委婉的請求,肯定答語分別是can/may/will.Could I sit here?Of course, you can.7.表示敢dare作為情態(tài)動詞時表示敢,用于疑問句或否定句;作為行為動詞時同其他動詞一樣用于各種句式,跟動詞不定式作賓語,在疑問句和否定句中可以省略to, I dare say是一個固定短語,意為“我認(rèn)為、我相信”。Tom darent go out alone when it is dark. (情態(tài)動

9、詞Tom doesnt dare (to go out alone when it is dark. (行為動詞8.表示應(yīng)該should 表示義務(wù)、責(zé)任、命令、勸告,意為應(yīng)該,ought to 表示義務(wù)、約束力、同should ,但是語氣比should強,比must 弱,must意為應(yīng)當(dāng)做。I should pay Tracy a visit, but Im not sure whether I will have time thisSunday.Humans ought to stop polluting nature.You must take the cost into consider

10、ation.9.表示命令、警告、威脅A.shall 與第二、三人稱連用表示命令、許諾、警告、威脅等,表示說話人強烈的意志.You shall get an answer from me by tomorrow.B.mustnt是must 的否定形式,表示禁止,是一種命令、威脅或警告。Tom, you mustnt leave all your clothes on the floor like this!10.表示驚訝、難以置信A.should 用于疑問句中可以表示驚訝、難以置信的事情Why should he tell a lie?B.can用于疑問句或否定句可以表示驚訝、不相信等感情色彩。

11、How can you say that you really understand the whole story if youhave covered only part of the article?11.表示寧愿would rather意為寧愿,后跟動詞原形,同used to, had better一樣也被看作是情態(tài)動詞,有時稱半情態(tài)動詞。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 oppos

12、ite.二、情態(tài)動詞+不定式完成時1. must have done表示對過去的事情肯定推測,意為:一定做過某事,只能用于肯定句。It must have rained last night, for the road is all wet.2. cant/couldnt have done都可使用在疑問句和否定句中表示推測,可看做must表推測對應(yīng)的否定形式,cant 比couldnt的語氣強,強調(diào)從現(xiàn)在角度出發(fā)推測過去某事的不可能性, 但當(dāng)主句的謂語動詞為過去式時,表示假定或推斷的從句必須用couldnt have done.We knew he couldnt have crossed

13、the river, because the bridge was broken and there was no boat.3. could have done表示過去有能力或有可能做某事,而因某種原因未做,有惋惜、遺憾、批評、責(zé)備的含義。He could have passed the exam, but he was too careless.4. should have done表示本該做某事,而實際上沒做,shouldnt have done 表示本來不應(yīng)該做某事,而實際做了。含有指責(zé)對方或自責(zé)的意味。I told your friend how to get to the hote

14、l, but perhaps I should have drivenher there.5. may/might have done用于對過去的事情進行推測,表明說話人對過去可能發(fā)生的行為或存在的狀態(tài)的一種懷疑,might表達的可能性比may要小得多。如果主句的謂語動詞是過去時,從句必須用might have done.表某事本來可能發(fā)生,而實際上未發(fā)生也只能用might have done.You might have read about it in the papers.6. need have done表示本來需要做某事而沒有做,neednt have done 則表示本來不需要做某

15、事而做了。I neednt have taken the umbrella, for the weather is fine.7. darent have done用在否定句中表示過去本來不敢做某事,但是現(xiàn)在敢做了。I darent have done it yesterday, but I think I dare now.8. was/were would like to have done表示本來打算做某事但是卻干了別的事。I would like to have gone to the party last night but I had to work extrahours to f

16、inish a report.9. would have done虛擬語氣,表示對過去事情的假設(shè),意為:本來會做。I would have told you all about the boys story, but you didnt ask me.形容詞和副詞的比較等級 1. 同級比較 A. 雙方比較程度相同的時候，用 as+形容詞或副詞的原級+as 這一結(jié)構(gòu)。 I think physics is as important as maths. B. 雙方比較程度不同等時，用 not+as/so +形容詞或副詞的原級+as 這 一結(jié)構(gòu)。 It is not as/so warm today

17、 as yesterday. C. 當(dāng)同級比較的形容詞與單數(shù)可數(shù)名詞連用時，應(yīng)注意不定冠詞的位置， 通常為：as+形容詞+a/an+單數(shù)名詞+as 這一結(jié)構(gòu)。 Would you like to join us? Sorry, Im not so good a player as any of you. 2. 比較級 A比較雙方中一方超過另一方的時候，要用 形容詞/副詞的比較級 +than+比較對象 這一結(jié)構(gòu)。 Zhang Hua is taller than Wang Ping. B. 表示不如用 less+原級+than 這一結(jié)構(gòu)。 The film is less interesting

18、 than that one. C. 除比較句中與 than 連用表示比較之外，下面的詞語后面必須用 to 構(gòu) 成比較，常用的詞有 inferior, superior, junior, senior, prior. He is superior to Mr. Wang in English. D. 表示兩個人/物之間比較的，用 the +比較級+n+of+the+名詞/代詞 這一結(jié)構(gòu)。 She is the taller of the two girls. E. 表示越來越用 形容詞比較級+and+ 形容詞的比較級； the+形容詞/ 副詞比較級，the +形容詞/副詞比較級。 It tur

19、ned warmer and warmer. The harder he works, the more progress he has made. F. 表示幾倍于時，用倍數(shù)+asas 或倍數(shù)+比較級+than Our classroom is three times larger than yours. G. 形容詞比較等級前可以用 much, very much, even, still, far 等來修飾， 表示比較的程度。 Toms handwriting is far better than Johns. H. 其他含有比較級的短語和句式 morethan與其說倒不如 more or less 幾乎、大約 more than less than 多于 少于 遲早、早晚 而且 一就 至多，不超過 僅僅、只不過 有之多 不少于 sooner or later whats more no sooner than not more than=at most no more than=only no less than =as many as not less than =not fewer than 3.