1、情态动词,情态动词 情态动词具有一定得词义，没有人称和数的变化，不能单独构成谓语，和谓语动词连用表示委婉语气或表示愿望、态度或推测等意义。,一、情态动词的类型和特征 情态动词的类型 只作情态动词的有：must; can(could);may(might) 只作情态动词也可作实义动词的有：need , dare 可作情态动词也可作助动词的有：will(would); shall(should) 具有情态动词的某些特征的有：have to; ought to; had better,2. 情态动词的特征 (1). 有一定的词义，但不能单独作谓语，必须和行为动词或系动词连用，构成谓语。 (2)表示说
2、话人的态度或语气，无人称和数的变化（have to例外，其第三人称单数形式为has to） He has to walk home. 情态动词后面跟的动词须用原形。,二、情态动词的用法 1. Can的 用法 常用来表示能力，意为“能，会”。 eg：She can swim fast, but I cant. 表示请求或许可，意为“可以”。 eg: Can you go shopping with us? 表示推测，意为“可能”，常用于否定句或者疑问句中，此时cant 意为不可能。 eg: Can the news be true？ That cant be our teacher. He is
3、 on a visit to the Great Wall.,-I think Miss Gao must be in the library. She said she would go there. -No.She _be there. I have just been there. A. cant B. mustnt C. neednt D. wouldnt,4） cant 可用来作May I .？的否定回答 -May I go surfing alone this afternoon? -No, you cant . Its dangerous. 5) can和 be able to
4、两者都是表示“能力”是用法相同，但can只有原形和过去式could两种形式，其他时态要用be able to来表示。另外，be able to常常有“成功做了某事”的意味 Jim cant speak English. We were able to reach the top of the maintain at noon.,2. Could 的用法 can的过去式，意为“能，会”，表示过去的能力。 eg: He could write poems when he was 10. could 在疑问句中，表示委婉的语气，此时could没有过去式的意思。 eg: Could you pleas
5、e speak a little louder? Could I use your pen? Yes, you can/ No, you cant .,-Could I cross the street here? -Of course you _. could B. can C. are able to D. will,3. may 的用法 may 表示请求、许可，意为“可以”，比can要正式。 eg：May I ask you a question? You may go home now. 表示推测，谈论可能性，意为“可能、也许”，一般用于肯定句。 eg：It may rain tomo
6、rrow. She may be at home. may 的过去式为might，表示推测，可能性低于may。 eg：He is away from home. He might be sick. (4) may表示祝福 May you be happy!,(5)can和may 1) Can和may均可用来征求意见或许可，意为“可以”，一般可互换使用 Can/May I help you? 2)may 和can 表示可能性时的区别： 在肯定句中用may, might, 不用can； 在疑问句中表示推测用can； 在否定句句中用cant（不可能） She may be in the classr
7、oom. Where can they be now? That cant be true.,(6) may be 和 maybe 用法区别 常用位置 may be may 为情态动词，be动词原形 句中，做谓语 maybe 副词，大概、也许， 相当于perhaps 句首，作状语 He may be wrong, but Im not sure.,-Have you decided which senior high school to choose? -Not yet. I _go to Moonlight School. A.must B.may C.need D. should -Wha
8、t will the weather be like tomorrow? -It _be rainy, cloudy or sunny. Who knows? must B. might C.shall D. should,情态动词练习 1讲解 1.-_I have a look at your new watch? -Yes, please. May B. Need C. Dare D. Must 2.Tom is young but he _fly a kite by himself. may B. can C. need D.must,3.The work is too hard for
9、 him. He _finish it on time. cant B. mustnt C. shouldnt D. neednt 4. The bookstore was open, so I _buy the book. can B. cant C. did can D. was able to,5. Last year I _drive. I used take the bus. could B. couldnt C. should D. shouldnt 6. -Could we smoke here? -Im afraid you _. couldnt B. cant C. are
10、able to D. will,7.-I hear youve got a new iPhone 4S._ I have a look? -Yes, certainly. May B. Do C. Shall D. Should 8.-Wheres Lucy? -Im not sure. She _in the school library. maybe B. must be C. may be D. will be,9.-Where is Tom? -_he is at home. He didnt feel well yesterday. May be B. Maybe C. May 10
11、.-_ I swim here? - Im sorry. Children _swim alone here Must; cant B. May; must Can; mustnt D. Cant; can,4. Must 的用法 must表示“一定要，必须”。否定形式是mustnt，表示 “禁止，不许可”。 eg：You must stay here until I came back. You mustnt park your car in front of the entrance. 对must引导的疑问句，肯定回答为must，否定回答为 neednt或者dont have to。 eg
12、：-Must I finish my homework now? -No, you neednt., must 常常指有根据的，比较有把握的推测，意为 “一定是，准是”，这种用法只能用于肯定句当中。 eg：The light is on. He must be at home now. 当must表示肯定判断、推测的时候，其反意疑问句要用实际问句的助动词来构成。 eg：She must have finish writing, hasnt she?, must 和have to must侧重于个人意志和主观上的必要，意为“必须，应 该”。 eg：I know I must study hard
13、. have to 侧重于客观上的必要，意为“不得不”。它有一 般现在时第三人称单数形式has to 和过去形式had to。 eg：My brother was very ill, so I had to call the doctor at midnight. have to的否定形式是dont have to, 相当于neednt, 意为“不必”；mustnt 表示“禁止，不允许”.,(5) cant 和 mustnt 表否定推测时应用cant, mustnt 意为“禁止，不允许”，不用来表推测，在肯定句中用must表推测，意为“一定”,- Mom, must I clean my ro
14、om now? - No, you _.You can do it tomorrow. cant B. neednt C. mustnt D. shouldnt,5.need 的用法 need表示“需要，必须”，主要用于否定句和疑问句当中，否定形式为neednt,意为“没有必要，不必”。用need提问时，肯定回答是must，否定回答为neednt. eg：-Need I stay here any longer? need可作实义动词，此时还有人称，数和时态的变化，后面多接动词不定时。 eg：I need to do it right now. He needs to learn more a
15、bout the girl.,注意： 对need 的词性判断常为难点，need后加to do说明need为实义动词，用助动词提问或否定；need后加doing表示被动意义；若need 后加do的动词原形，则need为情态动词 You neednt see him, but I must. You dont need to come if you feel sick.,(6). dare 表示 “敢于”， 用作情态动词时，无人称变化，只用于否定句、疑问句和条件句 Mary dare not touch the snake. 用于实义动词时，要注意人称和时态的变化，后面跟不定式 I have ne
16、ver dared to tell him about it. 注意：dare作实义动词时，其疑问句或否定句后面的不定式符号常省略。 He didnt dare (to) disobey.,You _ swim in this part of the lake. Its dangerous. mustnt B. neednt C. wont D. may not I enjoy the party very much, but I _ go home. Its too late. A . have to B. may C. mustnt D. shouldt,6. shall, should,
17、 will, would的用法 shall常用于疑问句当中，表示征求对方的意见（多用于第一、三人称），用在第一人称或第三人称的疑问句中 eg：shall we go out for a walk? Shall he come at once? 一般回答： Yes, please./ All right./ No, thank you. Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。 eg: You shall fail if you dont work harder. （警告） He shall have the book when I finish reading.
18、（允诺） He shall be punished. （威胁）,should意为“应该”。可表示劝告、建议、义务、责任等。 eg：We should protect the environment., will表示主语的决心或意愿；也可表请求或询问，用于第二人称。 eg：I will never do that again. I will help you if Im free this afternoon. Will you pass me the book? will表示习惯、请求，固有性质等。 eg: Everyday he will sit here hour after hour d
19、oing nothing.（习惯） Will you help me with my English?（请求）,7. had better的用法 had better 意味“最好”，没有人称的变化，后接不带to的不定式，其否定形式为had better not. eg: We had better go now. You had better not give the book to him.,- How was the youth club last night, Mark? -It was great fun. You _have come. Must B. can C. should D. may You look tired now. You _stay at home and have a rest. had to B. had better C. would like to D. would rather,PS: 在英语中，我们可以用其他多种方式提出我们的建议或征求对方意见。 (1).用“Lets do.”来提出建议。 e.g. Lets go for a walk a
