must,can,may,should,would,need和shall的區(qū)別

1、1. can (could)1)表示能力，could 主要指過(guò)去時(shí)間。Two eyes can see more than one. 兩只眼比一只眼看得清。Could the girl read before she went to school?這女孩上學(xué)前能識(shí)字嗎？2)表示可能(理論上或是邏輯判斷上)。The temperature can fall to 60c , that is 60 C below freezing.氣溫可降至60，也就是零下60。He can' t (couldn ' t) have enough money for a new car.他不可能有

2、足夠的錢買新車。You mustn' tsmokewhile you' rewalking around in the wood. You could start a fire.在林子里走時(shí)勿吸煙，那樣可能會(huì)引起火災(zāi)。3)表示允許。Can I have a look at your new pen? 我可以看一看你的新鋼筆嗎？He asked whether he could take the book out of the reading room.他問(wèn)他可不可以把書帶出閱覽室。4)表驚異、懷疑、不相信等態(tài)度。主要用于否定句、疑問(wèn)句或感嘆句中。Where can (could

3、) they have gone to? 他們會(huì)去哪兒了呢？He can' t (couldn ' t) be over sixty.他不可能超過(guò)六十歲。How can you be so careless? 你怎么這么粗心？5)比較委婉客氣地提出問(wèn)題或陳述看法。Can (Could) you lend me a hand? 幫我一把好嗎？I ' m afraid we couldn ' t give you an answer today.恐怕我們今天不能給你答復(fù)。2. may (might)1)表允許，might 可以指過(guò)去時(shí)間，也可指現(xiàn)在時(shí)間，語(yǔ)氣更委婉。

4、You may take whatever you like. 你喜歡什么就拿什么。He told me that I might smoke in the room.他告訴我可以在房間里抽煙。May (Might) I ask for a photo of your baby? 我可以要一張你寶寶的照片嗎？在回答以may引起的問(wèn)句時(shí)，多避免用這個(gè)詞，而用其它方式，如Yes, please./ Certainly./ Please don t ./ You ' d better not. / No, you mustn ' t.等，以免顯得太嚴(yán) 峻或不客氣。2)表可能(事實(shí)上)

5、?？梢灾高^(guò)去時(shí)間，也可以指現(xiàn)在時(shí)間，但語(yǔ)氣更加不肯定。He may be at home. 他可能在家。She may not know about it. 她可能不知道這件事。He was afraid they might not agree with him.他擔(dān)心他們可能不同意他的意見。m not sure. 他們有可能在開會(huì)，不They might be having a meeting, but I 過(guò)我不肯定。3. must1）表示義務(wù)。意為“必須”（主觀意志）。We must do everything step by step. 我們一切都必須循序漸進(jìn)地做。You mustn

6、' t talk to her like that.你不可能那樣對(duì)她說(shuō)話。-Must we hand in our exercise books now? 我們現(xiàn)在就要交練習(xí)本嗎？-No, you needn t. / No, you don t have to. 不必。（這種情況下，一般不 用 mustn' t）2）表示揣測(cè)。意為“想必、準(zhǔn)是、一定”等，只用于肯定句。He must be ill. He looks so pale. 他準(zhǔn)是病了。他的臉色蒼白。She s wearing a diamond n ecklace. She must have a lot of m

7、oney. 她戴著鉆石項(xiàng)鏈，一定很有錢。4. shall1）表征詢意見，用于第一、第三人稱疑問(wèn)句。Shall I get you some tea? 我給你點(diǎn)茶好嗎？Shall the boy wait outside? 讓那男孩在外面等嗎？What shall we do this evening? 我們今晚做什么？2）表說(shuō)話人的意愿，有“命令、允諾、警告、決心”等意思，用于第二、第三人稱陳述句。You shall do as I say. 按我說(shuō)的做。（命令）You shall have my answer tomorrow. 你明天可以得到我的答復(fù)。（允諾）He shall be sor

8、ry for it one day, I tell you.有一天他會(huì)后悔的，我告訴你。（警告）Nothing shall stop us from carrying out the plan.什么也不能阻止我們執(zhí)行這項(xiàng)計(jì)劃。（決心）5. will1）表意愿，用于各種人稱陳述句。I will do anything for you. 我愿為你做任何事。None is so blind as those who won ' t see.不愿看的人眼最瞎。If you will read the book, I ' ll lend it to you.如果你愿意讀這本書，我會(huì)把它借

9、給你。2）表請(qǐng)求，用于疑問(wèn)句。W川you close the window? It ' s a bit cold.請(qǐng)你把窗戶關(guān)上好嗎？有點(diǎn)冷。Won t you drink some more coffee?再來(lái)一點(diǎn)咖啡好嗎？3）表示某種傾向或習(xí)慣性動(dòng)作。Fish will die out of water. 魚離開水就不能活。The door won t open. 這門打不開。The boy will sit there hour after hour looking at the traffic go by.那男孩常常坐在那里好幾個(gè)鐘點(diǎn)，看著車輛行人通過(guò)。6. should1）表

10、義務(wù)。意為“應(yīng)該”（某件事宜于做），用于各種人稱。You should be polite to your teachers.你對(duì)老師應(yīng)該有禮貌。You shouldn t waste any time.你不應(yīng)該浪費(fèi)時(shí)間。2）表推測(cè)，意為“想必一定、照說(shuō)應(yīng)該、估計(jì)”等。The film should be very good as it is starring first class actors.這部新電影是一流演員主演的，估計(jì)拍得很好。They should be home by now. 照說(shuō)他們現(xiàn)在應(yīng)當(dāng)已經(jīng)到家了。1）表意愿。They would not let him in beca

11、use he was poorly dressed.他們不讓他進(jìn)我說(shuō)過(guò)我愿意為你做任何事。再來(lái)杯啤酒好嗎？ 請(qǐng)把窗戶擦一下好嗎？去因?yàn)樗轮婆f。I said I would do anything for you.2）表委婉地提出請(qǐng)求、建議或看法。Would you like another glass of beer?Would you mind cleaning the window?They wouldn ' t have anything agai nst it.他們不會(huì)有什么反對(duì)意見。3)表過(guò)去反復(fù)發(fā)生的動(dòng)作或過(guò)去的一種傾向。Every time she was in tr

12、ouble, she would go to him for help. 她每遇到麻煩都會(huì)向她求助。他告訴我盒子打不開了。(二)情態(tài)動(dòng)詞后跟完成式和進(jìn)行式的用法1 .情態(tài)動(dòng)詞后跟完成式，表”應(yīng)當(dāng)已經(jīng)”，”想必已經(jīng)”，”本來(lái)可 以”等意。I should have finished the work earlier.我應(yīng)當(dāng)早一點(diǎn)完成這項(xiàng)工作的。He isn ' t here. He must have missed the train.他還未到，一定是沒(méi)趕上火車。Where can (could) he have gone? 他能到那里去了呢？You may (might) have r

13、ead about it. 你可能在報(bào)上已經(jīng)讀到這件事了。You could (might) have been more careful. 你本來(lái)可以更細(xì)心的。He needn' t have worried about it.他本不必為此事?lián)?。There was a lot of fun at yesterday' s party. You ought to have come, butwhy didn ' t you?昨天的聚會(huì)非常有意思。你本應(yīng)該來(lái)，為何不來(lái)呢？2 .情態(tài)動(dòng)詞后跟進(jìn)行式，表示“想必正在”，”可能正在”，”應(yīng)當(dāng)正在”等意。It ' s t

14、welve o ' clock. They must be having lunch.現(xiàn)在是十二點(diǎn)。他們一定正在吃飯。They may be discussing this problem. 他們可能正在論討這個(gè)問(wèn)題。He can' t be telling the truth.他說(shuō)的不可能是真話。She shouldn t be working like that. She ' s still so weak.她不應(yīng)當(dāng)那樣干，她身體仍那么虛。(三)幾組詞的辨異1. can 和 be able to1) 情態(tài)動(dòng)詞can 只有兩種時(shí)態(tài)形式，現(xiàn)在式 can 和過(guò)去式coul

15、d ， 而 be able to有多種時(shí)態(tài)形式。Mary can play the piano. She has been able to play it since she was 5.瑪麗會(huì)彈鋼琴。她五歲起就會(huì)彈了。2）用在過(guò)去時(shí)中，could經(jīng)常表示能夠做某事，事實(shí)上不一定去做，而was/ were able to 則表示“過(guò)去做成了某事”。在否定句中兩者可通用。He could swim across the English Channel. But he didn ' t feel like it that day.他能游過(guò)英吉利海峽，但那天他不想游。Yesterday I

16、was able to get home before the heavy rain.昨天我在下大雨前趕到了家里。2. must 和 have tomust表示主觀意志，而have to表示由于客觀因素不得不做某事。must沒(méi)有過(guò)去式， 除在間接引語(yǔ)中可用于表示過(guò)去時(shí)間，在直接引語(yǔ)中表示過(guò)去時(shí)間應(yīng)該用had to 代替。I told her that she must give up smoking.我叫她必須戒煙。We had to get everything ready that night.我們那晚得把一切準(zhǔn)備就緒。3. would 和 used to1） used to 表示過(guò)去與現(xiàn)在或過(guò)去某時(shí)與后來(lái)的情況有不同，而would 只表過(guò)去的情況。People used to think that the earth w