单击此处编辑母版标题样式,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,情态动词,情态动词（,model verb）,用来表示能力、允许、可能、必须、劝告、意愿等概念或态度主要的情态动词有,can（could），may（might），shall（should），will（would），must，ought to，need，dare,等情态动词没有人称和数的变化，其后常跟不带,to,的不定式1.,情态动词的一般用法：,(1),表示能力:,can,could,be able to,He is over 80 but still can read without glasses.,She couldnt come yesterday.,He cant come tomorrow.,l,can/could,与,be able to,用法比较,1）,be able to,除有一般现在时、一般过去时、一般将来时外，还可有现在完成时、不定式、动词-,ing,形式等This is the information Ive been able to get so far.,To be able to ride a bike,she practiced a lot.,Just being able to drive a horse,a cart isnt much help to us.,2),could,表示过去总的、经常性的能力；,was/were able to,表示过去具体情况下具有的能力，并且做了某动作。
He could speak French,so he was able to show the French lady the way.,3),表示将来的能力常用,will be able to.,When will you be able to take us to town?,(2),表示许可：,can/could,may/might;cant,may not,mustnt,must not,1)征询“许可”或给予“许可”可用,can/could,或,may/might,表示May,用于正式场合，,can,用于非正式场合，,could,用于客气的询问，,might,极少用You can go at four oclock.,Could I borrow your pen?,Students may take 3 books each.,Might I ask whether you are using the typewriter?,2),表示“不允许”用,cant,may not,mustnt；must not,语气重You cant leave the table unless you finish your meal.,Put that cigarette out.You must not smoke near a petrol pump!,3),表示过去“许可”不用,could，might，,要用其他表达方式。
We had been/were given permission to speak to the patient.,但在间接引语中表达过去“许可”，可用,could，mightThe nurse said that we could/might speak to the patient for just a few minutes.,(3),表示可能性：,may/might,can/could,must;cant,1）,may,might,用来推测现在“可能”；,may,比,might,表示的可能性大些Why isnt John in class?He may/might be sick.,maybe,是副词，不是情态动词Maybe he is sick.,2),在日常口语中常用,can/could,表示“可能”You can/could walk for miles in the country without meeting anyone.,Can the news be true?No,it cant be true.,3)must,表示可能性最大，“必定”；否定形式用,cant,表示“肯定不”、“必定不会”。
You must be hungry after a long walk.,The phone is ringing,but there is no answer.She cant be at home.,（4）表示必须和需要：,must,have to,need,1）,must,表示说话人认为“必须”；否定回答时用,neednt“,不必”You must be here at nine oclock.,Must you go soon?No,I neednt go yet.,2)have to,表示他人或客观情况要求“必须”I have to be back at school by eight.I have a lot of work to do tonight.,We dont have to wear uniforms in school.,l,口语中常用,have got to,表示“必须”I have got to leave now.I have a meeting in ten minutes.,3),need,表示动作者“需要”、“有必要”，用于否定句或疑问句；肯定回答用,must，,否定回答用,neednt。
Need he go now?Yes,he must.No he neednt.,l,need,常用作实义动词You need to learn the value of time.,You didnt need to tell him the news.,Does she need to go?,（5）表示责任和劝告:,should,ought to,must,had better,1),用,should,和,ought to,表示责任和劝告，后者的语气重些,You should/ought to do as you are told.,Such things shouldnt/ought not to be allowed.,2),有时也用,must,表示责任和劝告You must see the movie.Its wonderful.,3),口语中也常用,had better,表示劝告，意为“最好做/不做某事”You had better take care of yourself.,Youd better not make a mistake next time.,Hadnt you better see who is at the door?,（6）表示建议：,shall，may/might as well,may/might just as well,1),“,shall I/we”,表示征求对方对建议的看法。
Shall we carry the boxes into the house?,Lets go,shall we?,2),may/might as well,may/might just as well,表示推荐更佳方案，建议另一种做法，意为“倒不如”，“不也一样吗？”We may as well stay here tonight.,You might just as well tell the truth,.,(7),表示许诺：,shall,shall,用于第二、三人称，表示说话人的许诺You shall have your money back next week.,If he passes the exam,he shall have a holiday.,(8),表示意愿：,shall,will/would,1),you/he/they shall,表示说话人的强烈意愿，甚至威胁You shall pay for this.,They shall do what I tell them to do.,l,在法律条文、规章制度中，,shall,表示“必须”Each competitor shall wear a number.,2,),will/would,表示动作者愿意。
I will lend you the book if you need it.,I wont do it again.,I have been trying to open the door,but the key wont turn.,l,“will you/would you”,在下列句中表示客气的建议、询问Will you please have a drink?,Would you please pass me the salt?,Would you like a cup of tea?,Would you mind if I opened the window?,Would you mind opening the window?Would you mind my opening the window?,l,would,还表示过去的习惯等于,used to,On Sundays he would get up early and go fishing.,(9)表示勇敢：,dare,dare,表示“敢于”，用于否定句、疑问句或条件句He dare not try.,How dare you open the letter?,If you dare say a word,Ill strike you down.,l,dare,还常用作实义动词。
He dare to surf in heavy waters.,l,daresay,或,dare say，,表示,probably,I suppose.,I dare say he will come home late.,2.,情态动词的特殊用法,（1）,情态动词+不定式完成时,1）,can/could,may/might,must+have+,动词的过去分词,用于肯定句：表示对过去事件的主观判断，推测过去某动作“可能”、“也许”、“一定”已发生Tom could have taken the dictionary.I saw him using it last Sunday.,I cant find my sunglasses.I may/might have left them at the restaurant yesterday.,You screamed in your sleep last night.You must have had a terrible dream.,用于否定句：表示推测过去某动作“可能”、“也许”、“一定”没有发生She couldnt have finished her work so soon.,She may not have seen you.,Dad mustnt have washed the dishes last night.,2),should/ought to+have+,动词的过去分词。
用于肯定句：评论过去“应该做”而实际并未做的动作，意为“本应该”I didnt ask her.Its a pity.You should have asked her.You ought to have asked everyone.,用于否定句：评论过去“不应该做”而实际做了的动作，意为“本不应该”I only told Mike.You shouldnt have told anyone.You ought not to have t。