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1、 情态动词Modal Verbs情态动词是什么？动词类别系动词情态动词助动词行为动词能独立做谓语不能独立做谓语情态动词是什么？n必须要和其他动词连用；n可表示说话人的语气，用来表达建议、要求、可能和意愿等；n没有人称和数的变化。常用情态动词n现在式 can 过去式 could （能，可能）n现在式 may 过去式 might （可以）n现在式 shall 过去式 should （应该）n现在式 will 过去式 would （会，将要）nmust 无时态之分nhad better、dare、need、ought to情态动词can/could1.can表现在的能力 I can swim,but
2、 my sister cant.2.could表过去的能力 At that time we thought the story could not be true.3.You cannot smoke in the meeting room.(此句的cannot 表示“禁止”)情态动词can/could3.can/could 与be able to 相比be able to 可用于各种时态，表能力，强调成功地做某事was/were able to:设法做成某事 相当于managed to do sth suceeded in doing sth情态动词may/might1.may表示请求别人允
3、许e.g.May I use your bike?2.may/might表示可能性e.g.He may be a teacher.3.may用于表示,应该(多用于法律条文）e.g.Payment may be paid by check.情态动词shall/should1.用于第一、三人称，征求对方意见 e.g.Shall we go now?What should we do next?(用should 比 shall 表示更客气)2.shall 用于法律、规定，表示义务和规定8.g.The sign reads:No person shall smoke here!3.should表示应该
4、 e.g.You should not judge a man by his clothes.情态动词 will/would1.用于向第二人称征求对方意见(would 比 will 更客气)e.g.Would you please open the door?2.will表示个人主观意愿e.g.I will help you anytime.3.would“表过去常常”e.g.When he was there,he would go to that coffee shop every day.注：used to do“过去常常，强调现在不了”情态动词 must1.must 表必须e.g.Yo
5、u must keep the place clean.(务必)mustnt 禁止e.g.When I was young,I was told that I mustnt play with fire.2.must 还可表示“偏偏，偏要”e.g.Must you make so much noise?情态动词 must/have to1.must 表示主观意愿，否定句用mustnt，否定回答用neednte.g.You mustnt play in the street.Must I clean the room now?No,you neednt.2.have to表示客观条件的限制的“不
6、得不”，它有时态和人称变化，需要助动词来否定和疑问。e.g.I dont have to carry the big box.He had to wash his clothes.情态动词表推测可能性的强弱层次must should/ought to can/could may/might1.should/ought to表示推测根据经验的推测，“应当、应该”e.g.Your photos should be ready by12:00.表示“竟然”，带有感情色彩e.g.It is incredible that you should like him.can/could 表推测1.常用于否定
7、句和疑问句 e.g.He cant be at home.(否定句)Can the news be true?(疑问句)2.can 用于肯定句中表示理论上的可能性，并不涉及是否真的会发生e.g.You can hurt yourself if you play in the street.may/might表推测1.may well”极有可能”e.g.Liza may well not want to go on the trip,because she dislikes travelling.2.may/might as well”不妨”e.g.You may as well try to do it.can?may?must?could?might?1.Jim _can_ sing very well.2.Hello,_may/might_ I speak to Jim?3.We are students.We _must_ work hard.4._may/might_ I come in?5.You _can_ talk in class.