1、<p>Modal Verbs（情态动词）情态动词的特征1. 情态动词后面一般接原形动词（ought to. have to. used to本身带有 to）2. 情态动词一般没有人称和数的变化。3. 情态动词有一定的词义，但不能单独作谓语，它们要和行为动词或系动词连用，构成谓语；4. 情态动词具有助动词的作用，即可用来构成否定句、疑问句及用于简明答语。（A）can1.表示能力 could主要指过去时间。Could the girl read before she went to school?2.表示客观可能（理论上或是逻辑判断上）。It can be interesting to
2、 go out for a walk.3.表示请求允许Can /Could I have a look at your new pen? Yes,you can/No,you cant.（只能原型 can回答）此时可与 may互换，在疑问句中还可用 could ,might 代替，不是过去式，只是语气更委婉，不能用于肯定句和答语中。4.表示推测，通常用于否定句、疑问句、可以和 could 互换，can 表推测，不能用肯定句。Tom cant/couldnt be back in the United States, for I saw him in the street just a mome
3、nt ago.5.表示“经过努力才可以做成功某事”时通常用 be able toHe was able to go to the party yesterday evening in spite of the heavy rain .对比点cancould1、表“能力”Can you lift this heavy box?I couldnt understand what he saidat all.2、表“允许”You can use a different materialinstead.He said I could borrow his bike.3、“推测”No, no, it c
4、ant be true.We thought the story could not betrue. How could you be soWhat on earth can this mean?careless?4、can 与 beable to 区别1. could 代替 can，表示语气更为婉转。Eg. Could I use your bike?Yes, I can2. can (能够)=be able to(仅表能力时)，但 be able to 表示一番努力后，才能做得到，且有更多的时态。（B）may （might）1. 表示请求和允许 might 比 may语气更委婉，而不是过去
5、式。2. 表示推测、可能性（不用于疑问句）。might 不是过去式，它所表示的可能性比较小。对比点maymight1表“询问”May I ?(=Can I ?)Might I ?(=Could I?)(但比用 may 更客气)2.表“允许”You may take the boy there.He told me he might come.(might 与 told 相呼应)3表“可能”“或许”She may nor like this place.Im afraid he might not like thisplay.注：1. May I?的答语。2. may 可表示期望或祝愿May y
6、ou succeed !3. may (might) 用于目的状语从句。肯定：Yes, you may.否定：No, you mustnt 不行（语气强硬）No, you may not 或 No, youdbetter not.The emperor gave them some goldin order that they might begin theirwork at once.（C）must表示义务、命令或必要，意为“必须”注意答语: - Must we hand in our exercise books today ?- Yes , you must . No , you don
7、t have to / you neednt.2 2mustnt 表示明令禁止，“千万别，不许，一定不要”表示推测，“非得，偏偏”对比点musthave to1. 表“必须”（主观看法）必须；没有过去式，可用于间接引语中。He told me I must do accordingto what he said.（客观需要）不得不，有多种时态。Its raining heavily, we cantgo now.2. 疑问句Must I ? Yes, you must.（一定）No, you neednt./ you donthave to.(不必)Do you have to go toda
8、y?Yes, we do.You dont have to worry aboutthat.（D）will1. 表意愿，愿望，决心2. 表请求，建议对方做某事，用于疑问句，与第二人称连用。3.表示某种倾向或习惯性动作Fish will die out of water . 鱼离开水就不能生活。（F）shall1.Shall 用于第一、三人称，表示提议或征求意见2.Shall 用于第一、三人称，表示说话人给对方的命令、警告威胁，允诺或决心。3.表示宣布法律或规定shallwill1. 征询对方意见或请求指示，用于第一、三人称：Shall I (we)? Shall he(she)?Where s
9、hall I (we)wait for you?1. 询问对方的意思或向对方提出要求：Will you (please)? Wont you?Would you like to.? (would 替代 will更客气)Wont you go and see the film?你不去看电影吗-Yes, I think I will. 不， 我想去。2. 表示说话人的“意愿”有“命令”“警告”“强制”“允诺”“决心”等，用于第二、三人称。You shall do what I tell you ( to do).我叫你干什么你就干什么。Everything shall be done to sav
10、e theship.一定要竭尽全力来拯救这艘船。2. 表示“意志”“意愿”，用于各种人称：I wont do anything you dont like.我不会做任何你不喜欢的事。Would表示过去时间的“意志”“意愿”Shylock would not take the moneyearlier.夏洛克先前是不肯要钱的。（E）wouldwould 表示过去反复发生的动作或某种倾向 would 表示过去习惯时比 used to 正式，且没有“现已无此习惯”的含义。1表示估计和猜想2表意愿3表委婉地提出请求，建议或看法。used towould1.表示过去的动作、状态，重在与现在情况的对比，不
11、一定要有时间状语。I used to play cards a lot, but now I1.只表示过去动作的重复，有明确的时间状语。I would go to see my grandfather onSunday when he was in the middleseldom play.My hometown is not what it used to be.school.2.would 后只接表动作的动词，不接表认识或状态动词He used to be nervous in the exam.2. 表示过去的习惯有时可互换：When we were very young, we us
12、ed to / would go skating every winter.3. 表示过去的次数时，不能使用：(）We went to the Great Wall five times when we were young.(X) We used to go / would go to the Great Wall five times when we wereyoung.注：used to do 的否定式：usednt to do 或 didnt use to do (usednt 也可写作usent)疑问式： Did you use to do ?Didnt you use to do?
13、Used you to do?Usednt you to do?（G）should可表示“义务”、“要求”或“转告”，常译作“应该”、“应当”表示“竟然”It is quite astonishing that he should speak to you like that .对比点shouldought to1、表“应该”表劝告、建议You should listen to the doctorsadvice.We should learn from ZhangHua.“有责任有必要”做某事You ought to finish your workbefore you go home.We
14、 ought to help each other.2、表“估计”They should get home by now.“非常可能”的事，可译为“总应该”If we start to work right now, weought to finish it before lunch.注：1）should 还可在虚拟语气中的使用2) 注意：ought to 的疑问式及否定式-Ought he to go? -Yes, I think he ought to. -No, he oughtnt to.否定式：oughtnt to do (不说 ought to not do) 反疑问句：ought
15、nt_?总结：大多数情态动词（除表能力、许可、意志外），都可以表示推测，其程度有差异。按可能性程度的高低排列为：must（完全肯定）willwould （完全可能）ought toshould （很可能）cancould（可能）maymight （有可能）补充：1). could + have + P.P.表示本来能做到，但事实上没有做到。2). couldnt +have + P.P.表示本来不能做到，但已经做到了。3) neednt + have + P.P.表示本不必做的，但已经做到了。4.) should/ought to +have + P.P.表示该做而没有做5) shouldnt/ oughtnt to +have + P.P.表示不该做而做了。</p>
