1、情态动词I. 情态动词基本用法：在英语中主要的情态动词有can (could), may (might), must, have to, need , ought to, dare (dared), shall (should), will (would) .1情态动词的特征（1）情态动词本身有词义，但词义不完成，因此不能单独作谓语，只能和其他的动词原形一起构成谓语。（2）情态动词后接的动词不定式一律不带to。（3）情态支词不随人称变化而变（即不管是何人称，后面接的情态动词都一样）。（4）含有情态动词的否定都是由“情态动词+not”构成的，如：can-can not may-may not n
2、eed-need not(5)含有情态动词的疑问句的构成May I come in?我可以进来吗？ Can you lend me some money?你能借给我一些钱吗？注意：含有have to 的句子变成疑问句时不同。如：I have to go today,今天我必须走，Do you have to go today?你今天必须走吗？2情态动词的用法（1）Can的用法表示体力或脑力方面的“能力”Can you drive?你会开车吗？Can you speak English?你会说英语吗？Can you lift heavy box?你能将这个重箱子拎起来吗？ 表示客观条件允许You
3、 can skate on the lake.(The ice is thick enough.)你可以在湖面上滑冰了（冰层够厚的了）The airplane can take off now.(The storm has stopped.)飞机可以起飞了（暴风雨停了） You cant park your car here. 你不能在此停车can用在否定句和疑问句中时，有时表示说话人的怀疑，惊异、猜测或不肯定：no, no, it cant be true.不，不，这不可能是事实How can you be so careless!你怎么会这么粗心He cant be in the libr
4、ary。他现在不会在图书馆注意：a,在口语中can常可用来代替may,来询问或说明一件事能不能做b, can 和 be able to在表示能力这一点是同义词，I can speak English.=I am able to speak English.l Could是 can的过去式，可以用来表示过去的能力或“可能性”I could run very fast when I was young. 我年轻时跑得很快I couldnt understand what he said at all. 我一点也听不懂他说的话表示惊异、怀疑How could you be so careless?
5、你怎么会这样粗心We thought the story could not be true. 我们当时以为那个故事不会是真的。可以代替can用于现在的动作，但语气较为婉转，如：Could I use your bike?我可以用一下你的自行车吗？You could do it this way.你可以把这个男孩带去（2）may的用法用来询问或表示允（在此用法中may和第一人称连用时都以疑问句形式出现）May I ask you a question?我可以问你一个问题吗？You may take the boy there.你可以把这个男孩带去。 He may come if he like
6、s.如果他想来，可以来They may stay in our house.他们可以在我家歇息。表示说话人的猜测，认为某一事情“或许”或“可能”发生We may call on you this evening我们也许今天晚上会来看你（们）She may not like this place她可能不喜欢这个地方l Might 是 may的过去形式，表示询问或允许或可能、推测等。如：Might I give you a piece of advice?我可否给你提个建议（Might 比 may更客气）He told me he might come.他说他可能来（Might与told相呼应都是
7、过去式）I was afraid he might not like this place.我当时担心他可能不喜欢这个地主（Might 与was相呼应，都是表示过去。【注意】：A。有时Might也可用来表示现在的事情，只是语气较may更弱一些，可能性更小一些，如：He might know her address. 他也许知道她的地址。Be careful, you might break it. 小心点，要不你可能会将它打碎BMay(might)后加动词不定式的完成式可以表示对过去的推测、认为某事在过去“可能”发生，这一用法中may和might都指过去，不过might较may更含蓄或更不肯定
8、。如：He may (might) have watched TV the whole night.(For he looks very sleep)他可能看了一夜电视（因为他看上去非常困倦）They might ( may) not have caught the train.他们可能没赶紧上车。（3）must的用法表示“必须”或“应当”。如：We must rely on ourselves.我们必须依靠自己You must finish the work before four oclock.你必须在四点前干完这项工作【注意】：A，在回答用must引的的疑问句时，否定结构只能用needn
9、t如：Must I do this? No, you neednt Yes, you must.B，在表示“必须”这个意思时，must的意思和have to是很接近的，只是have to 比较强调客观需要，而must侧重说明主观看法，在下面情况下两都就不宜换用：Its raining heavily, we cant go now. I think well have to wait till the rain stops.雨下得太大了，我们现在无法走，我想我们只能等雨停了再走We must ask for permission if we do it.如果我们要干，一定要先征得同意。must
10、只有现在式而无其他时态变化，通常也只用来表示现在，但有时出可以用must表示过去（多用在间接引语中），如：He told me I must do according to what he said. 他对我说，我必须按他说的做。must也可表示推测，但比may肯定得多，可译成“一定”或“准是”，如：He must be in the library.他现在准在图书馆It must be four in the morning now.现在一定是到了清晨四点钟了（4）have to的用法后接动词原开，表示“不得不、必须”的意思，它比must更含有“客观条件使得必须如此做”的意思。并有较多的时态
11、，如：We have to get up early.我们不得不早起We will have to get up early tomorrow. 我们明天必须早起We had to get up early at that time. 我们那时不得不早起【注意】：在口语中常用have got to 来取代have to，如： Ive got to stay here.我不得不留在这里（5）ought to 的用法表示“有义务或有必要”作某事You ought to finish your work before you go home.你每天回家前应把工作做完You ought not to
12、be so careless. 你不应当这样粗心表示非常可能的事His father ought to know his address.他你亲总该知道他的地址吧If we start work right now, we ought to finish it before lunch.如果我们现在开始干，午饭前应当能干完ought to 后接动词不定时的完成时，如用肯定结构，表示过去某事该做而未做，如用否定结构，则表示过去不该做的事情发生了。You ought to have been more careful.你应当更仔细些才是（但事实是当时没有仔细行事）You ought not to
13、have interrupted them.你当时不应当打断他们（的谈话），（但当时的事实是打断了别人的谈话。）【注意】：此用法相当于”should (not) have done”结构（6）dare的用法dare 表示“敢”的意思，它的过去时是dared除在”I dare say”这种结构中，dare极少用作肯定结构中的情态动词一般用在否定句和疑问句中，其用未能和其他情态动词一样，即dare 不随人称变化而变，后面所跟的动词不定式不带to。如：I dare not tell the truth.我不敢照实说出Dare she go out alone at night?她敢一个人夜间出去吗？
14、Dare也有实义动词形式，在现在英语中，dare用作实义动词的时候更多一些。（7）need的用法need表示“需要”，其用未能与dare 几乎完全相同，即用于否定句和疑问句中，本身无变化。在肯定句中通常用need有实义动词形式，用法同其他实义动词一样，如：Need we do it again?我们需要再做一次吗？No, you neednt do it again.不，不需要重做。I think he needs to do it again.我认为他需要重新做一次。（此句中的needs是实义动词。）【注意】：A，当实主动词形式的need用于疑问句和否定句中时，和其他实义动词的用法一样。如：
15、Does he need to do it again? No, he doesnt need to do it again.B, need后面有名词或动名词作宾语地，need是实义动词，但后接动名词的句子相当于被动语态，如：We need some more hands. 我们需要更多的帮手The garden needs cleaning.(=The garden needs to be cleaned.) 院子要清扫了The flowers need watering.(=The flowers need to be watered.) 花要浇水了（8）shall的用法主要用于第一人称的
16、疑问句中，表示征求对方意见。如：What shall I do now?我现在该干点什么Shall we go together?咱们一起走好吗(9) should的用法表示“劝告、建议”，译作“应当”You should study hard.你应当努力学习You should listen to the doctors advice.你应当听大夫的话We should help each other.我们应当互相帮助表示“推测、可能”They should get home by now.他们现在该到家了The book should be available in the booksto
17、re.这本书在书店里可能有卖的后接动词不定式的完成式时，表示过去的事情，肯定结构表示该做没做；否定结构表示不该做，但发生了。I should have written you earlier.我应当早引起给你写回信（但没写）You shouldnt have told him this.你不应当把这告诉他。（但告诉了）(10) will, would的用法主要用于第二人称的疑问句中，表示说话人向对方提出请求，would较 will更客气些Will you help me? 你能帮帮我吗？Would you like some tea? 你想喝点茶吗？Will you please tell m
18、e the way to the station? 请问到车站怎么走？(11) used to的用法后接动词原形，表示以前经常发生的动作，但现在不是这样了（通常用于肯定句中）。I used to get up early，我以前经常早起（现在不是这样了）He used to read aloud everyday. 他以前天天朗读（但现在不是了）注意：句型“be + used to”后接动名词或名词，表示“习惯“：I am not quite used to the weather, here. 我不大习惯这里的天气Are you used to the food in Beijing?你现在
19、习惯吃北京的饭了吗？ Im used to getting up early.我习惯早起。II. 情态动词must, may, might, could, can表示推测：以must为例。must + do(be)是推测现在存在的一般状态进行；must + be doing 推测可能正在进行的事情；must +have done是推测可能已经发生过的事情。1. must“肯定，一定”语气强，只用于肯定句中。He must be a man from America. / He must be talking with his friend. / He must have already arr
20、ived there.2. may和might“也许”，后者语气弱，更没有把握。可用于肯定句和否定句。He may not be at home. / They might have finished their task. 3. can和could“可能”，could表示可疑的可能性，不及cant语气强，用于肯定、否定、疑问句中。The weather in that city could be cold now.We could have walked there; it was so near.（推测某事本来可能发生，但实际上没有发生）Can he be in the office no
21、w? No, he cant be there, for I saw him in the library just now.(语气很强，常用于疑问句和否定句中)【注意】：1.对现在的事实进行推测：主要结构：must / may / might +动词原形be+名词/形容词/介词短语be + doing例句：1. You must be Jeanne. Im Mathilde Loisel. We used to know each other very well. 2. They must be in bed already at this time of the night.3. The
22、teacher must be joking.4. Freda isnt in class. She must be sick.5. There must be something wrong.6. She might be very clever, but she hasnt got much common sense.7. He may be arriving this evening.8. He may be traveling around the world.9. The keys cant be in the room. I have just searched it very c
23、arefully.10. Can the news be true ?2对过去的事实进行推测：结构：情态动词+have done / been+名词/形容词/介词短语。例句：1. Mrs. Longmans must have been a pretty girl in her youth.2. He couldnt have seen Anna yesterday. Shes gone abroad.3. I think I must have left my glasses in the library.4. He might have overslept again.5. Where c
24、an Tom have gone ?.情态动词表达虚拟语气：表达“本来”，“不然早就”。这是情态动词的一种虚拟语气用法。表示说话人所讲的与所发生的事实相反。表达了说话人的埋怨，后悔的语气。其结构是在一些情态动词后面加 have done 结构。根据要表达的意思，有如下结构：(1).should have done / ought to have done：本应该(2).shouldnt have done / oughtnt to have done：本不该(3).could have done：本来可以(4).neednt have done：本来没必要(5).would like to h
25、ave done：本来很想(6).would rather not have done: 本来不愿意(7).could / might / have done: 不然早就例句：1. You shouldnt have laughed at his mistakes. 2. You could have told us earlier.3. You ought not to have spent so much time in reading novels.4. We need not have been in a tearing hurry to catch the train.5. They
26、 would like to have seen that film last film.6. If he had given me his number, I could have telephoned him.7. They might have been frozen to death but for the rescue in time. 情态动词注意点：1. can和be able to: 都可以表示能力。但be able to可以表达“某事终于成功”，而can无法表达此意。Be able to有更多的时态。另外，两者不能重叠使用。2. used to和would: used to表
27、示过去常常做现在已经不再有的习惯，而would只表示过去的习惯或喜好，不涉及现在。3. need和dare作情态动词和实义动词的区别：两者作情态动词时常用于否定句和疑问句。其形式为：neednt/darent do；Need/daredo?做实义动词时可用于肯定句，否定句和疑问句。其形式为：need(needs/needed)/dare(dares/dared) to do, dont(doesnt/didnt) need/dare to do注意：句型I dare say+从句。 意思是：我肯定 = Im sure或There is no doubt that+从句。例句：I dare say that my uncle will get the money if I die.
