广东省2016届高三二轮复习讲义：第五讲 情态动词

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第五讲 情态动词
情态动词的定义: 　　　　　　　　　　　　　　　　　
　　情态动词 (Model Verbs) ( http: / / www.21cnjy.com ) 又称为情态助动词 (Model Auxil-iaries)。英语中助动词主要有两类：一是基本助动词，如have, do, be；二是情态助动词，如may, must, need等。情态动词与其他动词连用表示说话人的语气。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。情态动词是一种本身有一定的词义,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 ( http: / / www.21cnjy.com )列: can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .
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 e 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？
　　How dare you treat us like that！你怎能那样对待我们！
　
情态动词的特点:　　
　　情态动词无人称和数的变化, 情态动词后 ( http: / / www.21cnjy.com )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。
　　He could be here soon. 他很快就来。
　　We can't carry the heavy box. 我们搬不动那箱子。
　　I'm sorry I can't help you. 对不起，我帮不上你。
　　
情态动词的用法:
一. 情态动词的基本用法
1. can、be able to 和could
①can和be able ( http: / / www.21cnjy.com )to都表示能力，can只有现在和过去时，而be able to则有更多的形式。但当成功地完成某一具体动作时，通常不用could而用was/were able to来表示。这时was/were able to 相当于managed to，表示经过一番努力，终于能够完成某事。如：
Can you use chopsticks
The wounded man sti ( http: / / www.21cnjy.com )ll was able to get to the village and was saved in the end.
②can和could
can和could都可以表示能力、 ( http: / / www.21cnjy.com )技能、许可、建议或请求和可能性。但比较委婉客气地提出问题或陈述看法，一般用could，回答时则用can。如：
Could you help me carry the bag
Can I help you
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 able to 来表示。
He could help us at all. 他完全可以帮助我们。
With the teacher' ( http: / / www.21cnjy.com )s 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。2-1-c-n-j-y
2. may/might
①may/might表示可能可以。但may比might可能性大。
如：-Why isn’t he in class
-He may be sick.(生病的可能性较大)
-He might be sick.(生病的可能性较小)
②may/might表示“允许”，may用于 ( http: / / www.21cnjy.com )现在时或将来时，might常用在间接引语中表过去时，但might也可用于现在时间，表示比较委婉的语气，回答用may。如：
He says we may leave.
He said we might leave.
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 said he might lend us some money. 他说他可以借给我们一些钱。
③may / might 表示建议或请求，但might比may 更客气，意思更肯定而无过去时态的含义。【来源：21cnj*y.co*m】
—May / Might I use your bike
—Yes, you can / may.
—No, you mustn’t
　may 否定式为 may not, 缩写形式是 mayn't.
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。
3. must
Must 必须,应该,一定 ( http: / / www.21cnjy.com ),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。
①must表示必须，应该，没有时态变化。如：
You must do everything as I do.
I must finish my work today. 我今天必须完成我的工作。
You mustn't 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
②must表示肯定的推测。如：
The light is still on, so he must be at home.
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。
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。
It's six o'c ( http: / / www.21cnjy.com )lock already, we must have been late again. 已经六点钟了，我们一定又迟到了。
③mustn’t 表示禁止做某事。如：
You mustn’t smoke in the office.
must 和 have to 的区别: must 表示说话人的主观思想, have to 表示客观需要。
He had to go becaus ( http: / / www.21cnjy.com )e of somebody's calling him that day. 那天他要走是因为有人叫他。
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)
4. have to
have to 表示“必须、不得不”， ( http: / / www.21cnjy.com )是由于某种外界(客观)原因而“必须”，“不得不”做某事，也可表示经常的或习惯性的事“必须”做。have to的否定形式表示不必。have to可用于多种时态中。如：www-2-1-cnjy-com
You will have to clean your own boots when you join the army.
I have to be at my office every evening.
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。
5. should / ought to
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。
Why should I meet him？为什么我要见他
ought 应当,应该后面跟带有 to 的动词不定式。
You ought to read ( http: / / www.21cnjy.com ) these books if you want to know how to repair the motorcar. 如果你想知道如何修理汽车,你应该读这些书。21cnjy.com
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 hav ( http: / / www.21cnjy.com )e taken the book out of the reading-room. 你不应该把书带出阅览室。www.21-cn-jy.com
①should和ought to表示应当、应该，前者比后者语气轻。如：
You should / ought to work hard.
②should / ought to的否定形式表示禁止之意。如：
Children shouldn’t smoke.
③should可表示陈述意见，推出建议或请求；而ought to可以表示劝告之意。如：
You ought to respect your parents.
He suggested that they should leave at once.
6. will / would
will (would)决心,愿望。 would 为 will 的过去式, 可用于各人称。
I'll do my best to catch up with them. 我要尽全力赶上他们。
I'll never do it again, that's 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。【来源：21·世纪·教育·网】
It's 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？给你来点咖啡怎样？
①will 用于各种人称表示“意志”、“意愿”或“决心”等，否定式won’t + 动词。如：
I will tell you all about it.
Tom won’t do such a thing.
②will用于疑问句中，常用在第二称时表示说话人向对方提出“请求”或“询问”如：
Will you please tell her the news when you see her 　　21*cnjy*com
③will 表示习惯性的动作，有“总是”、“惯于”的含义。如：
Fish will die out of water.
④would 表示客气的请求、建议或意愿。如：
Would you please be quiet
Would you like coffee
⑤would 表示过去反复发生的动作。如：
When I passed my s ( http: / / www.21cnjy.com )chool I would see my teachers who taught me 5 years ago.
7. need
need 作“必要”讲，既可作情态动词，也可作实义动词。作实义动词时后面的动词不定式要带to，其变化与一般动词相同。如：21世纪教育网版权所有
I need to think it over.
—Need you go now
—Yes, I must./No, I needn’t
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 ( http: / / www.21cnjy.com )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。21*cnjy*com
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。
needn't + have + 过去分词表示过去做了没必要做的事情。
You needn't have taken it seriously. 这件事情你不必太认真。
8. dare
dare表示“敢”的意思。作为情态动词时，主要用在疑问句和否定句中
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 cat 你敢抓小猫吗
dare除用作情态动词外,更多 ( http: / / www.21cnjy.com )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。后面可带to的不定式，此时to也可以省略。dare与need的用法相似。如：21·cn·jy·com
How dare you say that
She doesn’t date(to)ask her father.
Do you dare to walk in the dark 你敢黑夜走路吗？
He doesn't dare to ( http: / / www.21cnjy.com )tell the teacher what happened that day. 他不敢告诉老师那天发生的事。
9. used to
表示过去常常发生的动作或存在的习惯，但现在已不复存在了。如：
He used to smoke.
used to +v, be used to +v-ing和be used to +v
·used to +v意为“过去常常”，“ ( http: / / www.21cnjy.com )过去一直”；be used to +v-ing / n(名词)意为“习惯于”；be used to +v意为“被用来(做某事)”。
·used to只表示过去，而be used to +v-ing / n可表示现在、过去或将来。例如：
He used to smoke. Now he doesn’t.
He’s quite used to hard work / working hard.
The knife is used to cut bread.
10. shall
①shall作为情态动词用于第二、三人称，表示说话人的意愿，有“命令”、“警告、威胁、强制”和“允许”等意思。如：
We shall do as our teacher says.
You shall have the book as soon as I finish it.
②在疑问句中，shall用于征求对方的意见或请求指示，常用于第一、第三人称。如：
Where shall he wait for us
Shall we go out for a walk
二. 情态动词表示推测或判断的用法
对现在和未来的推测：
must + 动词原形
may / might + 动词原形
can /could can / could do
should 用来表示一种估计的情况“按理会/估计会”should do/be
对过去的推测：
must have done 肯定句
may / might have done 肯定句、否定句
can / could have done 否定句、疑问名(could可用于肯定句)
should have done 肯定句、否定句、疑问句
情态动词+行为动词完成式即“情态动词+ have + v-ed分词”，表示对过去行为或动作进行推测、评论或判断。2·1·c·n·j·y
　　(1) must have v-ed
must have v-ed ( http: / / www.21cnjy.com ) 表示推测过去某事“一定”发生了。其否定形式为：can’t / couldn’t have v-ed, 表示过去不可能发生某事。例如：
Since the ditch is full of water, it must have rained last night.
You couldn’t have met my grandmother. She died before you were born.
　　(2) could have v-ed
could have v-ed 表示推测过去某动作“很可能”发生了。例如：
“The dictionary has disappeared. Who could have taken it ”
“Tom could have taken it. He was alone yesterday.”
　　(3) may / might have v-ed
may / might have v-ed 表示推测过去某事“也许”发生了.may 比 might 表示的可能性在说话人看来稍大些。例如：
I can’t find my key ( http: / / www.21cnjy.com )s. I may / might have left them at the school yesterday.
　　(4) ought to / sh ( http: / / www.21cnjy.com )ould have v-ed 和 ought not to / shouldn’t have v-ed
ought to / should ha ( http: / / www.21cnjy.com )ve v-ed 和 ought not to / shouldn’t have v-ed 用于对已发生的情况表示“责备”、“不满”，分别表示“本应该”和“本不应该”。例如：
With all the work fini ( http: / / www.21cnjy.com )shed, I should have gone to the party last night.
You ought not to m ( http: / / www.21cnjy.com )ake fun of him. He is not the one you laugh at but learn from.
　　(5) needn’t have v-ed
needn’t have v-ed 表示过去做了某事，但没有做的必要，意为“本没必要”。例如：
You needn’t have waken me up; I don’t 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：【出处：21教育名师】
　　“I wonder how Tom knew about your past.”
　　“He must / could / may / might have heard of it from Mary.”
翻译：
It must have rained last night.
She may not be at home. = It is possible that she is not at home.
She can’t be at home. = It is impossible that she is at home.21教育名师原创作品
They should be there right now.
对现在正在进行的推测
情态动词+行为动词进行式(即情态动词+ be + v-ing形式)，表示推测或评论某动作现在是否正在进行。例如：
He must be playing basketball in the room.
She may be staying at home.
　　
对完成进行的推测
情态动词+行为动词完成进行式(即情态动 ( http: / / www.21cnjy.com )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：21教育网
They should have been meeting to discuss the problem. 【版权所有：21教育】
He may / might have ( http: / / www.21cnjy.com )been buying stamps in the post office when you saw him.
三. 情态动词在虚拟语气中的用法
情态动词用于虚拟语气中表示责备的感彩，用法如下：
(1)should have do ( http: / / www.21cnjy.com )ne表示“本来应该做某事而实际上未做”，而shouldn’t have done则表示“本不应该做某事而实际上做了”。如：
You should have told me about it earlier.
You shouldn’t have said such words to your parents.
(2)ought to have done也表示“本应该厖”而ought not to have done则意为“本不应该厖”。如：
You ought to have told me about it earlier.
You ought not to have said such words to your parents.
(3)needn’t have done表示“本无必要做某事而实际上做了”。如：
You needn’t have walked so quickly since time was enough.
(4)could have done表示“本来有可能厖而事实上未做到”。如：
I could have come on time, but my car broke on the way. 21·世纪*教育网
四. 用作情态动词的其他短语
would rather, woul ( http: / / www.21cnjy.com )d sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well等可用作情态动词。例如：
　The soldier would sooner die than surrender.
　 The brave soldier would as soon die as yield to such an enemy.
　I’d rather walk than take a bus.
　If you don’t like to swim, you may just as well stay at home.
　注：这些短语后一般直接跟动词原形.w ( http: / / www.21cnjy.com )ould (had) rather, would (had) sooner, would (just) as soon后可跟that 引导的从句，that 常省去，从句要用虚拟语气。对现在和将来的假设用过去时，对过去的假设用过去完成时。例如：
I would rather you came on Sunday.
I would sooner you hadn’t asked me to speak yesterday.
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