語法復(fù)習(xí)情態(tài)動(dòng)詞

1、一、區(qū)別1. 表示請(qǐng)求和允許：ca n, could, may, might.過去式使語氣更委婉，答語應(yīng)用原形。-Could I use your computer tomorrow morning?-Yes, you can.（否定回答可用： No, I ' m afraid not.）2. 表示推測(cè)：理論可能性can主觀可能性肯定句must, may ,might, （could）疑問句can/ could否定句can /couldnt（不可冃能、肯疋不 ）, may not （可能不）1）can表示理論上的可能性，指某事或情況可能發(fā)生，但并不說明實(shí)際上真的發(fā)生Childre n

2、can be very tiri ng.2）反意問句 He may know the plan,doesn ' he?You must have studied English beforehaven ' ybu?You can 'halve been caught in the rain last night, were you?情態(tài)動(dòng)詞+ do ,表示現(xiàn)在或?qū)恚?be doing）情態(tài)動(dòng)詞 + have done，表示過去（+have been doing）（+have been done）3. could & be able to在肯定句中could表示

3、過去有"能力”做， was / were able to表示過去有能力而且確實(shí)做成了某一件 事， 相當(dāng)于 man aged to do 或 succeeded in doing sth.The fire spread through the hotel very quickly but every one was able to get out.4. may / might（just ） as well do sth 還是好”、"不妨”You might as well tell me the truth.你還是把真相告訴我的好。5. must 禾口 have to1）mu

4、st表示的是說話人的主觀看法,而have to強(qiáng)調(diào)客觀需要。2） 否定形式含義不同。mustn '禁止，不許可，don ' t have t不必3）must 偏要（做令人不快的事）eg. Must you shout so loudly?6. shall 和 should1）表示說話人 征求對(duì)方意見 和向?qū)Ψ秸?qǐng)示，用于第 一、三人稱。When shall my father be able to leave hospital?shall 2）表示命令、警告、允諾或威脅以及說話人的決心（文件規(guī)定）。用于二、三人稱。You shall go with me （命令）/ You sh

5、all have the book whe n I finish it.（允諾） He shall be punished（威脅）/ Nothing shall stop me from doing it.（ 決心）1）表示勸告和建議“應(yīng)該”2）“按道理應(yīng)當(dāng)”“估計(jì)”（=ought to）They should be there by no w, I think.3）用于第一人稱表示說話人的一種謙遜、客氣、委婉的語氣。I should advise you not do that.我倒是勸你別這樣做。should 4）在條件句中表示“萬一”，主句不一定用虛擬語氣。Ask Tom to ring

6、 me up if you should see him. /Should I be free tomorrow, I' II come.5） Why / How + should結(jié)構(gòu)表示說話人對(duì)某事不能理解，感到意外、驚異等意思，意為"竟然”，也用在某些從句中。It seems so unfair that this should happen to me.這種事竟然發(fā)生在我身上真不公平。7. will 和 would1）表示意志和意愿。will指現(xiàn)在，would指過去。If you will listen to me, I' ll give you some ad

7、vice.2）表示請(qǐng)求、建議， would 比 will 委婉、客氣。 Will （Would ） you please pass me the book?3）表示習(xí)慣性動(dòng)作，"總是”"慣于”，will指現(xiàn)在，would指過去。Fish will die without water.Every evening, she would sit by the win dow, deep in thought.4）.表示功能，意為"能” 或"行”The machine won ' t wtolkut /open/lock.5）表示預(yù)料或猜想。It wou

8、ld be about ten whe n he left home.猜想他離開家時(shí)大約點(diǎn)。8. would & used to1）表示過去持續(xù)的狀態(tài)和動(dòng)作用used to; would不與表示狀態(tài)的動(dòng)詞（be）連用。There used to be a hospital here. / There would be a hospital here.（ x ）2）would常與often, sometimes, for hours 等表示時(shí)間的副詞（短語）連用。We would sit i n the yard every evening and liste ned to his st

9、ory.3）used to強(qiáng)調(diào)過去的行為同現(xiàn)在的對(duì)比，含有“過去怎樣，而現(xiàn)在卻不這樣了” 的含義.eg. He willnot spe nd the money on books as he used to.9. dare 和 need兩者作為情態(tài)動(dòng)詞都不用于肯定句，常用于否定句、疑問句和條件從句中。習(xí)慣用語I dare say（可能，或許，我揣測(cè)）除外。實(shí)義動(dòng)詞用法同于一般動(dòng)詞。但在否定句中，dare情態(tài)動(dòng)詞（常用于否、 疑和條件從句中）實(shí)義動(dòng)詞時(shí)態(tài)dare/dared dodare(s)/dared to do否定dare n' t/dared n'tdodo n'

10、 t/does n' t/did n't(to) do10 cannot / can /can never - too /enough 越 越好,再.也不過分”。注意這個(gè)句型的變 體 cannot eno ugh .如： You cannot be too careful whe n you drive a car.駕車時(shí)候,越小心越 好。11 usedn'或 did ' t use t為 used to (do) 的否定式。Tom used not to rise at six every morning.12比較： needn' t have don

11、e & didn ' t need to do She need not have come yesterday.她昨天本不必要來的。(但去卩來了)She didn ' t need to come yesterday.她昨天不必來。(實(shí)際上也沒來)二、咼頻考點(diǎn)( 情態(tài)動(dòng)詞+have done)情態(tài)動(dòng)詞現(xiàn)在完成式主要有兩個(gè)功能：表示已經(jīng)發(fā)生的情況和表示虛擬語氣。1表示對(duì)已發(fā)生情況的猜測(cè)1) must have+done,過去一定/肯定”對(duì)已發(fā)生情況的肯定推測(cè)否定形式為 can' t / couldn '過去分詞即2)must n't have+d

12、o ne (x)2) can' t / couldn '過去分詞,過去一定沒/肯定不/不可能” 3) may / might have + 過去分詞，可能做了”否定形式為2表示虛擬語氣。1) needn' t havedone ,(本沒必要做)表示做了不必做的事，2) should / ought to have +過去分詞，本應(yīng)該 ”過去應(yīng)該做而實(shí)際并未做的動(dòng)作3) should not /oughtn't tohave+過去分詞，本不應(yīng)該”表示本不應(yīng)該做某事但實(shí)際上做了4) can/ could have + 過去分詞，“原本可以 ”表示過去本來可以做但卻未做，5) would(/could/might/should have) + 過去分詞，“原本會(huì) ”(尤其在if引導(dǎo)的非真實(shí)條件句中對(duì)過去虛擬，主句中較常用)You did n't atte nd yesterday's mee