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

1、1. can (could)1)表示能力，could 主要指過去時間。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?這女孩上學前能識字嗎？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.在林子里走時勿吸煙，那樣可能會引起火災。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、疑問句或感嘆句中。Where can (could

3、) they have gone to? 他們會去哪兒了呢？He can' t (couldn ' t) be over sixty.他不可能超過六十歲。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。2. may (might)1)表允許，might 可以指過去時間，也可指現在時間，語氣更委婉。

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引起的問句時，多避免用這個詞，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 峻或不客氣。2)表可能(事實上)

5、。可以指過去時間，也可以指現在時間，但語氣更加不肯定。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.他擔心他們可能不同意他的意見。m not sure. 他們有可能在開會，不They might be having a meeting, but I 過我不肯定。3. must1）表示義務。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地做。You mustn

6、' t talk to her like that.你不可能那樣對她說話。-Must we hand in our exercise books now? 我們現在就要交練習本嗎？-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。意為“想必、準是、一定”等，只用于肯定句。He must be ill. He looks so pale. 他準是病了。他的臉色蒼白。She s wearing a diamond n ecklace. She must have a lot of m

7、oney. 她戴著鉆石項鏈，一定很有錢。4. shall1）表征詢意見，用于第一、第三人稱疑問句。Shall I get you some tea? 我給你點茶好嗎？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. 按我說的做。（命令）You shall have my answer tomorrow. 你明天可以得到我的答復。（允諾）He shall be sor

8、ry for it one day, I tell you.有一天他會后悔的，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)行這項計劃。（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，我會把它借

9、給你。2）表請求，用于疑問句。W川you close the window? It ' s a bit cold.請你把窗戶關上好嗎？有點冷。Won t you drink some more coffee?再來一點咖啡好嗎？3）表示某種傾向或習慣性動作。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鐘點，看著車輛行人通過。6. should1）表

10、義務。意為“應該”（某件事宜于做），用于各種人稱。You should be polite to your teachers.你對老師應該有禮貌。You shouldn t waste any time.你不應該浪費時間。2）表推測，意為“想必一定、照說應該、估計”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，估計拍得很好。They should be home by now. 照說他們現在應當已經到家了。1）表意愿。They would not let him in beca

11、use he was poorly dressed.他們不讓他進我說過我愿意為你做任何事。再來杯啤酒好嗎？ 請把窗戶擦一下好嗎？去因為他衣著破舊。I said I would do anything for you.2）表委婉地提出請求、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.他們不會有什么反對意見。3)表過去反復發(fā)生的動作或過去的一種傾向。Every time she was in tr

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

13、ead about it. 你可能在報上已經讀到這件事了。You could (might) have been more careful. 你本來可以更細心的。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?昨天的聚會非常有意思。你本應該來，為何不來呢？2 .情態(tài)動詞后跟進行式，表示“想必正在”，”可能正在”，”應當正在”等意。It ' s t

14、welve o ' clock. They must be having lunch.現在是十二點。他們一定正在吃飯。They may be discussing this problem. 他們可能正在論討這個問題。He can' t be telling the truth.他說的不可能是真話。She shouldn t be working like that. She ' s still so weak.她不應當那樣干，她身體仍那么虛。(三)幾組詞的辨異1. can 和 be able to1) 情態(tài)動詞can 只有兩種時態(tài)形式，現在式 can 和過去式coul

15、d ， 而 be able to有多種時態(tài)形式。Mary can play the piano. She has been able to play it since she was 5.瑪麗會彈鋼琴。她五歲起就會彈了。2）用在過去時中，could經常表示能夠做某事，事實上不一定去做，而was/ were able to 則表示“過去做成了某事”。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沒有過去式， 除在間接引語中可用于表示過去時間，在直接引語中表示過去時間應該用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備就緒。3. would 和 used to1） used to 表示過去與現在或過去某時與后來的情況有不同，而would 只表過去的情況。People used to think that the earth w