語法復(fù)習(xí)情態(tài)動(dòng)詞

1、 高二英語語法復(fù)習(xí) 情態(tài)動(dòng)詞一、區(qū)別1. 表示請(qǐng)求和允許: can, 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, Im 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cant/couldnt (不可能、肯定不)，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.

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

3、表示過去有“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managed to do或succeeded in doing sth.The fire spread through the hotel very quickly but everyone 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和have to 1) must表示的是說話人的主觀看

4、法, 而have to強(qiáng)調(diào)客觀需要。2）否定形式含義不同。mustnt禁止，不許可，dont have to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 shall have the book when I

5、 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 now, 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 me up if you should

6、see him. /Should I be free tomorrow, Ill 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would 1) 表示意志和意愿。will 指現(xiàn)在，would指過去。If you will listen to me, Ill give you some advice.2) 表示請(qǐng)求、建議，would比will委婉、客氣。

7、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 window, deep in thought.4). 表示功能， 意為“能” 或“行” The machine wont work/shut /open/ lock.5) 表示預(yù)料或猜想。It would be about ten when he left home.猜想他離開家時(shí)大約點(diǎn)。 8. would

8、& 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.( ×)2) would 常與often, sometimes, for hours等表示時(shí)間的副詞（短語）連用。We would sit in the yard every evening and listened to his story.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.

9、eg. He will not spend 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daren't/daredn't dodon't/doesn't/didn't (to) do 10 cannot / cant/c

10、an nevertoo /enough“越越好,再.也不過分”。注意這個(gè)句型的變體 cannotenough.如：You cannot be too careful when you drive a car.駕車時(shí)候, 越小心越好。 11 usednt 或didt use to 為used to （do） 的否定式。 Tom used not to rise at six every morning.12.比較： neednt have done & didnt need to doShe need not have come yesterday. 她昨天本不必要來的。（但卻來了） S

11、he didnt need to come yesterday. 她昨天不必來。（實(shí)際上也沒來）二、高頻考點(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····cant / couldnt have+過去分詞 即2） mustn't have+done（×）2）cant / couldnt have+過去分詞, “過去一定沒/肯定不/不可能”3）may / might

12、have +過去分詞, “可能做了” 否定形式為···· 2.表示虛擬語氣。1） neednt have + done , （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 didn't attend yesterday&