1、 情态动词是一种本身有一定的词义,但要与普通动词一起使用，给谓语动词增添情态色彩，表示说话人对有关行为或事物的态度和看法，认为其可能、应该或必要等。情态动词后面加动词原形。分类：情态动词有四类：只做情态动词：must,can(could),may(might),ought to可做情态动词又可做实义动词：need,dare可做情态动词又可做助动词：shall(should),will(would)具有情态动词特征：have(had) to,used to位置:情态动词在句中放在谓语动词之前, 谓语动词前若有助动词,则在助动词之前,疑问句中, 情态动词则在主语之前。I can see you.
2、Come here.我能看见你，过来吧。He must have been away.他一定走了。What can I do for you?我能帮你吗？How dare you treat us like that！你怎能那样对待我们！特点:情态动词无人称和数的变化, 情态动词后面跟的动词需用原形,否定式构成是在情态动词后面加 “not“。 个别情态动词有现在式和过去式两种形式 , 过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去，现在或将来。情态动词属非及物动词，故没有被动语态。He could be here soon.他很快就来。We cant carry the he
3、avy box.我们搬不动那箱子。Im sorry I cant help you.对不起，我帮不上你。基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想：What have you been doing since? （构成完成进行体，本身无词义）I am afraid I must be going. （一定要）You may have read some account of the matter. （或许已经）除此之外，情态助动词还有如下词法和句法特征：1） 除 ought 和 used 以外
4、，其他情态动词后面只能接不带 to 的不定式。如果我们把ought to 和 used to 看做是固定词组的话，那么，所有情态动词无一例外地只能接不带 to的不定式：We used to grow beautiful roses.I asked if he would come and repair my television set.2） 情态助动词在限定动词词组总是位居第一：They need not have been punished so severely.3） 情态助动词用于第三人称单数现在时的时候，没有词形变化，即其词尾无-s 形式：She dare not say what
5、she thinks.4） 情态动词没有非限定形式，即没有不定式和分词形式，也没有相应的动名词：Still, she neednt have run away.5） 情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间：Would you mind very much if I ask you to do something?She told him he ought not to have done it.6） 情态助动词之间是相互排斥的，即在一个限定动词词组中只能出现一个情态助动词，但有时却可以与 have 和 be 基
6、本助动词连用：You should have washed the wound.Well, you shouldnt be reading a novel.用法首先它是动词，而且不同于行为动词，行为动词表示的是可以通过行为来表达的动作（如写，读，跑） ，而情态动词只是表达的一种想法（如能，也许，敢） 。用法是：情态动词+行为动词原形例句：I can read this sentence in English.我能用英语读这句话。情态动词是一种本身有一定的词义,表示说话人的情绪,态度或语气的动词,但不能单独作谓语, 只能和其他动词原形构成谓语。We can be there on time to
7、morrow.我们明天能按时去那儿。May I have your name? 我能知道你的名字吗？Shall we begin now?我们现在就开始吗？You must obey the school rules.你必须遵守校规。情态动词数量不多,但用途广泛 ,主要有下列:can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would),have (to) ,had better.助动词(auxiliary)主要有两类：基本助动词(primary auxiliary)和情态助
8、动词(modal auxiliary)。基本助动词有三个：do, have 和 be；情态助动词有十三个：may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to. 上述两类助动词的共同特征是，在协助主动词构成限定动词词组时，具有作用词的功能：1） 构成否定式：He didnt go and neither did she.The meeting might not start until 5 oclock.2） 构成疑问式或附加疑问式：Must you leave right
9、 now?You have been learning French for 5 years, havent you?3） 构成修辞倒装：Nowhere can he obtain any information about his sister.Hardly had he arrived when she started complaining.4） 代替限定动词词组：A: Who can solve this crossword puzzle?B: Tom can.A: Shall I write to him?B: Yes, do.can 和 could 的用法1. 表示能力或客观可能性
10、，还可以表示请求和允许。如：Can you finish this work tonight?Man cannot live without air. Can I go now? Yes, you can.注意：could 也可表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用 can（即 could 不能用于现在时态的简略答语中） 。如：Could I come to see you tomorrow?Yes, you can. （否定答语可用 No, Im afraid not.）can 表示能力时，还可用 be able to 代替。如：Ill not be able to c
11、ome this afternoon.2. 表示惊异、怀疑、不相信的态度。 （主要用在否定句、疑问句或惊叹句中）Can this be true?How can you be so careless!This cannot be done by him.3. “can(could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑或不肯定。如：He cannot have been to that town.Can he have got the book?4. 用在疑问句及否定句中, 表示惊讶,不相信等.5. cannottooenough 表示“无论怎样也不过分“,“越
12、越好“may 和 might 的用法1. 表示许可。表示请求、允许时，might 比 may 的语气更委婉一些，否定回答时(口语中常用) no , you cant . or , yes, please 用 mustnt 表示“不可以” 、 “禁止” 、 “阻止”之意( 具有强烈禁止的意思)如：You may drive the car. Might I use your pen? No, you mustnt.用 May I . 征询对方许可在文体上比较正式，在口气上比较客气。在日常口语中，用Can I . 征询对方意见在现代口语中更为常见。2. 用于祈使句中表示祝愿。如：May you s
13、ucceed!3. 表示推测、可能（疑问句不能用于此意） 。He may be very busy now.4. “may(might) + have + 过去分词”表示对过去发生的行为的推测。如：He may not have finished the work.must 和 have to 的用法1. 表示必须、必要。 （must 表示主观多一些而 have to 则表示客观多一些）如：You must come in time.回答 must 引出的问句时，如果是否定的回答，不能用 mustnt，而要用 neednt 或 dont have to。 Must we hand in our
14、 exercise books today? Yes, you must. (No, you dont have to.)2. “must be + 表语”的结构表示推测，它的否定或疑问式用 can 代替 must。This must be your pen.3. “must + have + 过去分词”的结构常用在肯定句中，表示对过去发生的行为的推测。它的否定或疑问式用 can 代替 must。He must have been to Shanghai.4. have to 的含义与 must 相似，两者往往可以互换使用，但 have to 有各种形式，随have 的变化而定。must 与
15、have to 有下列几点不同： must 表示的是说话人的主观看法，而 have to 则往往强调客观需要。如：The play is not interesting. I really must go now.I had to work when I was your age. must 一般只表现在，have 则有更多的时态形式。 二者的否定意义不大相同。如：You mustnt go. 你可不要去。You dont have to go. 你不必去。 询问对方的意愿时应用 must。如：Must I clean all the room?注意：have to 也可拼做 have got
16、 to。dare 和 need 的用法1. need 表示“需要”或“必须” ，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用 must, have to, ought to,或 should 代替。如：You neednt come so early. Need I finish the work today? Yes, you must.注意：neednt + 不定式的完成式“表示本来不必做某事而实际上做了某事” 。如：You neednt have waited for me.2. Dare 作情态动词时，主要用于疑问句、否定句和条件从句中，一般不用在肯定句中。如：How dar
17、e you say Im unfair.He darent speak English before such a crowd, dare he?3. Dare 和 need 常用作实义动词，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare 后面通常接带 to 的不定式，在否定和疑问句中，dare 后面可接带to 或不带 to 的不定式。如：I dare to swim across this river.He does not dare (to) answer.Dont you dare (to) touch it!I wondered he dare (to) say
18、 that.He needs to finish it this evening.shall 和 should 的用法1. Shall 用于第一人称，表示征求对方的意愿。如：What shall we do this evening?2. Shall 用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：Shall we begin our lesson?When shall he be able to leave the hospital?3. 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。如：You shall fail if you dont w
19、ork harder. （警告）He shall have the book when I finish reading. （允诺）He shall be punished. （威胁）4. Should 表示劝告、建议、命令，其同义词是 ought to；在疑问句中，通常用 should代替 ought to。如：You should go to class right away.Should I open the window?Should 的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子： I should think it would be better to try it a
20、gain. 我倒是认为最好再试一试。 You are mistaken, I should say. 依我看，你是搞错了。 I should advise you not to do that. 我倒是劝你别这样做。 This is something I should have liked to ask you. 这是我本来想问你的。从以上例句可以看出：情态动词 should 用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。Should 还可以用在 if 引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由 should 加动词原形构成
21、，主句谓语却不一定用虚拟语气。如： Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。 If you should change your mind, please let us know. 万一你改变主意，请通知我们。 Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。此外，Why(or How) + should 结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会” 。如： Why should you be so late
22、 today? 你几天怎么来得这么晚？ Where is Betty living? 贝蒂住在哪里？ How should I know? 我怎么会知道呢？ I dont know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。5. “should + have + 过去分词”结构一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如： She should have finished it.I should have helped her, but I never could.You should have
23、started earlier.will 和 would 的用法1. 表示请求、建议等，would 比 will 委婉客气。如：Would you pass me the book?2. 表示意志、愿望和决心。如：I will never do that again.They asked if we would do that again.The door wont open3. 用 “will be”和“will(would) + have + 过去分词” 的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：This will be th
24、e book you want.He will have arrived by now.The guests would have arrived by that time.I thought you would have finished this by now.4. Would 可表示过去反复发生的动作或某种倾向。Would 表过去习惯时比 used to 正式，并没有“现已无此习惯”的含义。如：The wound would not heal.During the vacation he would visit me every week.5. 表料想或猜想。如：It would be
25、about ten when he left home.What would she be doing there?I thought he would have told you all about it.ought to 的用法1. Ought to 表示应该。如：You ought to take care of him.2. 表示推测。注意与 must 表示推测时的区别：He must be at home by now. （断定他已到家）He ought to be home by now. （不十分肯定）This is where the oil must be. （比较直率）Th
26、is is where the oil ought to be. （比较含蓄）3. “ought to + have + 过去分词 ”表示过去应做某事而实际未做。如：You ought to have asked him (but you didnt).这时，ought to 和 should 可以互相换用。注意：在美国英语中，ought to 用于否定句和疑问句时，to 可以省略。如：Ought you smoke so much?You oughtnt smoke so much.ought 和 should 的区别：1.ought 语气略强。2.should 较常用。3.ought 在美
27、国英语中用的很少，而 should 却相当常用。4.ought 属正式用语。used to，had better，would rather 的用法1. Used to 表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变。如：He told us he used to play football when he was young.在疑问句、否定句、否定疑问句或强调句中，可有两种形式：疑问句Did you use to go to the same school as your brother?Used you to go to the same school as your b
28、rother?否定句I usednt to go there.I didnt use to go there.Usednt 亦可拼作 usent，但发音皆为 ju:snt。否定疑问句Usent you to be interested in the theatre?Didnt you use to be interested in the theatre?强调句I certainly used to smoke, but it was a long time ago.I certainly did use to smoke, but it was a long time ago.其反意疑问句或
29、简略回答中，也有两种形式：She used to be very fat, didnt she? （口语+常用）/ use(d)nt she? （正式+ 过时）Did you use to play chess? Yes, I did.Used you to get up early in the morning? Yes, I did. (Yes, I used to.)2. Had better 意为“最好” ，后接不带 to 的不定式。如： We had better go now. Yes, we had (wed better / we had better).Hadnt we be
30、tter stop now? (Had we better not stop now?)I think Id better be going. （用于进行时态，表“最好立即 ”）You had better have done that. （用于完成时态，表未完成动作）注：had best 与 had better 同意，但较少用。You had better 用于同辈或小辈，对长辈不可用。3. Would rather 意为“宁愿” ，表选择，后接不带 to 的不定式。如：Id rather not say anything.Would you rather work on a farm?
31、Wouldnt you rather stay here? No, I would not. Id rather go there.由于 would rather 表选择，因而后可接 than。如：I would rather work on a farm than in a factory.I would rather watch TV than go to see the film.I would rather lose a dozen cherry trees than that you should tell me one lie.Id rather you didnt talk ab
32、out this to anyone. （句中的d rather 不是情态动词，would在此是表愿望的实义动词）can (could), may (might), 用法:can (could) 表示说话人能 ,可以, 同意,准许, 以及客观条件许可,could 为 can 的过去式。Can you pass me the books?你能给我递一下书吗 ?Could you help me, please?请问,你能帮助我吗?What can you do?你能干点什么呢?Can you be sure?你有把握吗?can 和 could 只能用于现在式和过去式两种时态, 将来时态用 be
33、able to 来表示。He could help us at all.他完全可以帮助我们。With the teachers help,I shall be able to speak English correctly.由于老师的帮助,我将能准确地讲英语。may (might) 可以, 表示说话人同意 ,许可或请求对方许可。You may take the book home.你可以把书带回家去.May I come in?我可以进来吗?May I use your dictionary?我可以用你的词典吗?You may put on more clothes.你可以多穿点衣服.He s
34、aid he might lend us some money.他说他可以借给我们一些钱。may 否定式为 may not, 缩写形式是 maynt.might 是 may 的过去式, 有两种用法, 一种表示过去式，一种表示虚拟语气, 使语气更加委婉, 客气或对可能性的怀疑。He told me he might be here on time.他说他能按时间来。Might I borrow some money now.我可以借点钱吗?He might be alive.他可能还活着。编辑本段must, need, ought to, dare (dared)用法Must 必须,应该,一定,
35、准是, 表示说话人认为有必要做某事, 命令, 要求别人做某事以及对事物的推测。must 用来指一般现在时和一般将来时 , 过去式可用 have to 的过去式代替。I must finish my work today. 我今天必须完成我的工作。You mustnt work all the time. 你不能老是工作。Must I return the book tomorrow? 我必须明天还书吗?After such a long walk, you must be tired. 走了这么长的路 ,你一定困了。He must be the man I am looking for. 他一
36、定是我要找的人。He had to go because of somebodys calling him that day. 那天他要走是因为有人叫他。must + have + 过去分词,表示现在对过去事物的推测。He must have told my parents about it.他一定把这件事情告诉我父母亲了。He must have received my letter now.他现在一定收到我的信了。Its six oclock already, we must have been late again.已经六点钟了，我们一定又迟到了。must 和 have to 的区别:
37、must 表示说话人的主观思想 , have to 表示客观需要。You must do it now.你必需现在就干。(说话人认为必须现在干 )I have to go now.我得走了。(客观条件必须现在走 )need 需要 多用在否定式或疑问句中.Need I attend the meeting tomorrow?我需要明天参加会议吗?You need not hand in the paper this week.这一周你不必交论文。need 是一个情态动词, 他的用法完全和其他情态动词一样, 但 need 还可当作实义动词使用, 这时 need 就象其他动词一样,有第三人称, 单复
38、数, 后面加带 to 的动词等特性。I need a bike to go to school.我上学需要一辆自行车。Do you need a dictionary?你需要词典吗?She needs a necklace.她需要一条项链。neednt + have + 过去分词 表示过去做了没必要做的事情。You neednt have taken it seriously.这件事情你不必太认真。dare 敢 多用在否定或疑问句中。The little girl dare not speak in public.小女孩不敢在公众面前说话。Dare you catch the little c
39、at?你敢抓小猫吗?dare 除用作情态动词外,更多的是当实义动词使用 , 用法同实义动词一样,要考虑人称, 单复数,时态等。Do you dare to walk in the dark?你敢黑夜走路吗？He doesnt dare to tell the teacher what happened that day.他不敢告诉老师那天发生的事。编辑本段ought，will ，Shall, should，have toought 应当,应该 后面跟带有 to 的动词不定式。You ought to read these books if you want to know how to rep
40、air the motorcar.如果你想知道如何修理汽车,你应该读这些书。You ought to bring the child here.你应该把孩子带来。ought + to have done 句型。指过去动作 ,表示一件事情该做而未做。You ought to have been here yesterday.你昨天就应该来。ought not to have done 句型。表示一件不该做的事情却做了。You ought not to have taken the book out of the reading-room.你不应该把书带出阅览室。will (would)决心,愿望
41、。 would 为 will 的过去式,可用于各人称。Ill do my best to catch up with them.我要尽全力赶上他们。Ill never do it again, thats the last time.我再不会做那件事情了,这是最后一次。He said he would help me.他说他会帮助我。will, would 用于疑问句表示说话人向对方提出请求或询问,用 would 比 will 更婉转,客气。Its hot. Will you open the windows?天气太热了,你能打开窗户吗 ?Will you help me to work it
42、 out?你能帮我解这道题吗?Would you like some coffee？给你来点咖啡怎样？Shall, should 表示命令,警告 ,允诺, 征求,劝告, 建议惊奇。You should hand in the exercise book.你应该交作业本儿了。This should be no problem.这应该没问题。Shall we go now.我们现在可以走了吗?Why should I meet him？为什么我要见他?have to,不得不,必须,表示客观条件只能如此, 而 must 则表示主观思想必须。I have to go now.我现在得走了。I have to cook for my child.我得给孩子做饭。You must be here on time next time.你下次一定要按时来。We must go to get the timetable ourselves.我们一定要自己去拿时刻表。
