情态动词相关知识

1、19/19HYPERLINK /参见：必修三UNIT1、2情态动词中还做助动词有：will，would ，shall，should实义动词：need，dare 一、情态动词是一种本身有一定的词义,表示讲话人的情绪,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 tomorrow. 我们改日能按时去那儿。 May I have your name? 我能明白你的名字吗？ 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。 二、情态动词数量不

2、多,但用途广泛,要紧有下列: can (could), may (might), must, need, / ought to, dare (dared), shall (should), will (would) .,has to /have/had to, had better情态动词的位置: 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. 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? 你要什么？

3、 How dare you treat us like that！ 你怎能那样对待我们！ 三、情态动词的特点: 一般情况下，情态动词无人称和数的变化, (has to,have to;shall第一人称 )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。 个不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，现在或今后。 He could be here soon. 他专门快就来。 We cant carry the heavy box. 我们搬不动那箱子。 Im sorry I cant help you. 对不起，我帮

4、不上你。 四、情态动词的用法: can (could) 表示讲话人能,能够,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,你能关心我吗? 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,今后时态用 be able to 来表示。 He could help us at all. 他完全能够关心我们。 With the teacher

5、s help,I shall be able to speak English correctly. 由于老师的关心,我将能准确地讲英语。 may (might) 能够, 表示讲话人同意,许可或请求对方许可。 You may take the book home. 你能够把书带回家去. May I come in? 我能够进来吗? May I use your dictionary? 我能够用你的词典吗? You may put on more clothes. 你能够多穿点衣服. He said he might lend us some money. 他讲他能够借给我们一些钞票。 may

6、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. 他讲他能按时刻来。 Might I borrow some money now. 我能够借点钞票吗? He might be alive. 他可能还活着。 Must 必须,应该,一定,准是, 表示讲话人认为有必要做某事, 命令, 要求不人做某事以及对事物的推测。 must 用来指一般现在时和一般今后时, 过去式可用 have to 的过去式代替

7、。 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? 我必须改日还书吗? 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

8、。 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. 他一定把这件情况告诉我父母亲了。 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. 差不多六点钟了，我们一定又迟到了。 must 和 have to 的区不: must 表示讲话人的主观思想, have to 表示客观需要。 You must do it now. 你必需现在就干。(讲话人认为

9、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. 单独用为实义动词Need I attend the meeting tomorrow? 我需要改日参加会议吗? 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,单复数, 后面加带 to 的动词等特性。 I need a bike to go to school. 我上学

10、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情况。 You neednt have taken it seriously. 这件情况你不必太认真。 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讲话。 Dare you catch the little cat? 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

11、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。 ought 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 repair the motorcar. 假如你想明白如何修理汽车,你应该读这些书。 You ought to bring the child he

12、re. 你应该把小孩带来。 ought + to have done 句型。指过去动作,表示一件情况该做而未做。 You ought to have been here yesterday. 你昨天就应该来。 ought not to have done 句型。表示一件不该做的情况却做了。 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。 would 为 will 的过去式, 可用于各人称。 Ill do my best to catch up with t

13、hem. 我要尽全力赶上他们。 Ill never do it again, thats the last time. 我再可不能做那件情况了,这是最后一次。 He said he would help me. 他讲他会关心我。 will, would用于疑问句表示讲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 out? 你能帮我解这道题吗? Would you like some coffee？ 给你来点咖啡如

14、何样？ Shall, should表示命令,警告,允诺,征求,劝讲,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. 我们现在能够走了吗? Why should I meet him？ 什么缘故我要见他? 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. 我得给小孩做饭。 You mus

15、t 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。情态动词 (Model Verbs) 又称为情态助动词 (Model Auxil-iaries), 要紧有can, may, must, could, might, shall , should, will, would, ought to, need, dare等。情态动词与其他动词连用表示讲话人的语气。情态动词可表达建议、要求、可能和意愿等。情态动词没有人称和数的变化。在大学英语考试中，情态动词部分重

16、点测试以下内容： （1）情态动词+动词完成式: must have done （2）情态动词+动词进行式: must be doing （3）情态动词+动词完成进行式: must have been doing （4）某些情态动词的专门用法: need 一、情态动词+动词完成式 情态动词+动词完成式即“情态动词+ have + done分词”，表示对过去行为或动作进行推测、评论或推断。 1. must have donemust have done 表示对过去某事的确信推测。其否定或疑问形式都用can(could) 来表示. 例如： Since the road is wet, it must

17、 have rained last night.He cant have missed the way. I drew him a map.“The dictionary has disappeared. Who could have taken it?”因此对现在发生或今后发生的情况,要用must do 表示推测, 否定为cant do.He must understand that we mean business.You must be hungry after a long walk. 2.may / might have done may / might have done 表示推测

18、过去某事“也许”发生了.may 比 might 表示的可能性在讲话人看来稍大些。例如：I cant find my keys. I may / might have left them at the school yesterday.3. could have done 在确信句型中, 往往用作委婉的批判. 本应该做什么,而没做; 有时也用作推测.You could have told us earlier.Tom could have taken the dictionary.4. ought to / should have done和 ought not to / shouldnt ha

19、ve done ought to / should have done 和 ought not to / shouldnt have done 用于对已发生的情况表示“责备”、“不满”，分不表示“本应该”和“本不应该”。例如： 1）With all the work finished, I should have gone to the party last night. 2）You ought not to have made fun of him. He is not the one you laugh at but learn from. 5. neednt have done need

20、nt have done 表示过去做了某事，但没有做的必要， 意为“本没必要”。例如： You neednt have waken me up; I dont have to go to work today. 注：表示推测过去某动作发生的可能性时，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如： “I wonder how Tom knew about your past.” “He must / could / may / might have heard of it from Mary.” 二、情态动词+动词进行式 情态动词+行为动词进行式（即情

21、态动词+ be + doing形式），表示推测或评论某动作现在是否正在进行。例如： 1）He must be playing basketball in the room. 2）She may be staying at home. 三、情态动词+动词完成进行式 情态动词+行为动词完成进行式（即情态动词+ have been + v-ing 形式），表示推测或评论过去某动作是否正在进行或一直在进行。例如： 1）They should have been meeting to discuss the problem. 2）He may / might have been buying stamp

22、s in the post office when you saw him. 四、某些情态动词的专门用法 1. need 考试中要紧测试 need 作情态动词与作实义动词的区不.情态动词need与实义动词need 在时态、确信、否定结构上的对比见下表。时态 情态动词need 实义动词 need 现在时 He need (neednt) doNeed he do.? He needs (doesnt need) to do 过去时 He needed (didnt need) to do 今后时 He need (neednt) doNeed he do.? He will (not) need

23、 to do 注: need 一般用于否定句或疑问句. 2. dare 考试中要紧测试dare作情态动词和作实义动词的区不。情态动词dare 与实义动词dare 在时态、确信、否定、疑问结构上的对比见下表。句型 情态动词dare 实义动词 dare 确信句 现在时 dare to 少用过去时 dare to 少用 现在时 dare/dares to do过去时 dared to do 否定句 现在时 darent/dare not do过去时 dared not do 现在时 do/does not dare (to) do过去时 did not dare (to) do 疑问句 现在时 Da

24、re he do? 过去时 Dared he do? 现在时 Do you/Does he dear (to) do? 过去时 Did he dare (to) do 3. can 和 may考试中要紧测试can，may或could，might表示可能性的区不及对may构成的疑问句的回答。 （1）can, could, may, might都能够表示可能性.can, could表示潜在的可能性或理论上或逻辑推断上存在的可能性；而may, might则表示事实上的可能性。此外，can还具有“有能力”的意思，而may与might则不具此意。例如： According to the weather

25、forecast, it may rain tomorrow. Any man with a little sense can see that he is wrong. （2）May I / we ？这一类疑问句的确信回答为Yes, please.或Certainly；否定回答为Please dont.或No, you mustnt. 例如： “May we leave now?” “No, you mustnt. You havent finished your home work yet.” 4. can 和 be able to can 与 be able to 都能够表示能力，但两者

26、在用法上有点差异：can (could)表示主观能力，不表示意愿，它的今后时用will be able to; be able to表示主观意愿，强调要克服困难去做某事。例如： 1）My grandma is over seventy, but she can still read without glasses. 2）He is able to give up his bad habits. 5. must 和 have to must 和 have to 都能够表示“必须”，但有几点区不： （1）must 强调“内在的职责”、“义务”，而have to 强调“外界压力”、“不得已而为之”。 （2）have to可用于多种时态，而must一般用于现在时，其过去时与今后时分不由had to与shall / will have to代替。 （3）在回答must引起的问题时，假如是否定的答复，不能用mustnt，而要用neednt或dont have to，因为mustnt是“一定不要”、“一定不能”的意思。例如： 1）You must come to the classroom before eight. 2）It is raining hard outside, but I have to leave now. 3）“Must we d