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情态动词的定义和特点：
1. 情态动词表示说话人的态度和看法，认为可能、应该或必要等，情态动词本身有意义：
e.g. You may have read some account of the matter. （或许）
We can be there on time tomorrow. 我们明天能按时去那儿。(能力)
May I have your name? 我能知道你的名字吗？ （容许）
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。
2. 情态动词后面加动词原形：
e.g. Still, she needn"t run away. （他完全没有必要走。）
3. 情态动词无第三人称和单复数的变化。
e.g. She dare not say what she thinks.
4. 情态动词是不及物动词，无被动语态。
5. 过去式用来表达更加客气、委婉的语气。
e.g. Would you mind very much if I ask you to do something?
你介意不介意我请你做些事情？
6. 时态性不强。
e.g. She told him he ought not to have done it.
她（当时）告诉他，他不应该做了那些事情。
7. 倒装：
e.g. Nowhere can he obtain any information about his sister.
8. 省略和替代动词：
e.g. A: Who can solve this crossword puzzle?
B: Tom can.
A: Shall I write to him?
B: Yes, do.
III. Function and Usage功能与运用:
1. ability能够(做或达到)： “can / could / be able to”
1) “can, could” (人或物做主语) ---- (of a person or thing) general ability
e.g. The hall can seat 1,000 people. 这个大厅能坐1 000人。
He can drive a bus. / What can I do for you?
Can you play the piano?
He could play football well when he was 10.
We can"t carry the heavy box.
I"m sorry I can"t help you.
2) ‘be able to do"（人做主语）– instant ability 具体的、一次性的能力
e.g. I was not tired and able to swim across the river. (instant ability)
I"ll not be able to come this afternoon.
2. possibility 能够：（客观可能性）: “may / might / can”
1) “can” expresses “theoretical possibility逻辑上的可能性”；
e.g. He is in poor health. He can be ill at any time.
Can you finish this work tonight?
Man can not live without air.
2) “may” – “possibility” occurs only in statements 不在否定句中用P283
e.g. It may be true. 那可能是真的。
The road may be blocked. 这条路可能不通了。
He looks pale. He may be ill.
He said he might be late. 他说他可能会迟到。
“may” 比 “might” 的可能性要大。
Note When “may” is used in a question or negative sentence, it has a different meaning.
e.g. “You may not take it.” –> “你不可以拿走。”
“May I take it home？ –> “我可不可以把它拿回家？”
3) “might” conveys greater uncertainty in tone than “may” 更加不肯定的语气
e.g. It might rain, and again it might not. 天可能下雨，也可能不下雨。
The soft music might calm your jutters.
柔和的音乐或许能使你紧张的情绪安定下来。
** may (just) as well / might (just) as well: “不妨做”, “还是…为好”, might 比may 语气更委婉，根据情形选择。
e.g. Catherine, you may as well come too. 凯瑟琳，你不妨也去。
If that"s the case, I may as well try. 如果情况如此，我不妨试一试。
You might just as well tell me the truth. 你还是对我们说实话的好。
We might just as well get round the table. 我们不防围着桌子坐下。
3. permission 表示请求和允许：“can / could / may / might / must”
1) can / could
e.g. -- Can I go now? -- Yes, you can.
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?
“-- Could I come to see you tomorrow?
-- Yes, you can.” （否定答语可用No, I"m afraid not.）
could语气委婉，主要用于疑问句，答语应用can.
2) may / might
might比may的语气更委婉，否定回答时(口语中常用) no , you can"t. or, yes, please
e.g. “-- May I use your dictionary? -- Yes, please.”
“-- Might I use your pen? -- No, you can"t. ”
You may drive the car.
You may take the book home.
“-- May I come in? -- Yes, please.”
“---Where can he be?” “—He may / might be in the office.”
(用May I ... 比较正式、客气。在口语中，常用Can I ... 征询对方意见。)
3) mustn"t表示“不可以”、“禁止”、“阻止”之意(具有强烈禁止的意思)如：
e.g.“May I take this magazine out?” “No, you mustn"t.”
“我可以把这本杂志借走吗?”“不, 不行。
4. obligation义务性的必须: “must / have to / ought to / should”
e.g. The children must be back by 4 o"clock.
You must remember to write home.
We mustn"t waste our time.
You ought to have asked him (but you didn"t).
这时，ought to和should可以互相换用。
Ought you smoke so much?
You oughtn"t smoke so much.
1）must最强，ought语气略强、正式，should较常用。
2）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)
You must come in time.
I have to go now. 我得走了。(不想走，但客观条件必须走。)
3）回答must引出的问句时，如果是否定的回答，不能用mustn"t，而要用needn"t或don"t have to。
e.g. — Must we hand in our exercise books today?
— Yes, you must. (No, you don"t have to.)
4）在疑问句中，通常用should
e.g. Should I open the window?
5) 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。
e.g. She should have finished it.
He should have helped her, but he never could.
You should have started earlier.
Why must you always bother me?
5. special feelings表示惊异、怀疑、不快、失望等态度和感情：“should / can / could”
(to denote emotional feeling of displeasure, surprise, wonder, disappointment, etc.)
e.g. It"s a pity (that) they should lose the game so soon. (disappointment)
How should he speak such rude words to his mother? (surprise)
It is unbelievable that he should be working so hard.
How could I know? 我怎么会知道呢？
Why should you be so late 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 don"t 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。
6. prediction 预见: “will”:
e.g. This will be the book you want.
He will have arrived by now.
He will be a different person when he lives in England.
7. intention / resolution / will / warning: 说话人的意愿 / 意图 / 决心 / 警告:
“shall, will”
(Note: used for the 2nd and 3rd persons包括用于第二和第三人称作主语)
e.g. You shall stay with us as long as you like.
= I"m willing to let you stay with us as long as you like.
He shall be praised if he works hard this term.
= I"ll see that he is praised if he works hard this term.
I will never do that again.
They shall not pass. == We won"t let them pass. （warning）
You shall fail if you don"t work harder.
He shall be punished.
He shan"t come here == I won"t let him come here.
You shall obey my orders. == I insist that you obey my order.
He shall leave the country at once. == I insist that he leave the country at once.
8. ask for advice征求意见： “shall”
e.g. What shall we do this evening?
Shall we begin our lesson?
Let"s go together, shall we?
9. politeness / euphemism / modesty: 礼貌 / 委婉 / 谦虚: “should, would”
e.g. Would you pass me the book?
Would you kindly show me the way to the station? 你可以指点我去车站的路吗?
If you would kindly wait here a minute, I"ll ring the director"s office.
I should think it would be better to try it again. 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。
10. repeated action 重复的动作：“will, would”
e.g. He would sit for hours doing nothing. 过去他常常坐几个钟头什么事也不做。
He would come to see us on Sundays. 过去星期天他经常来看望我们。
She will dance for hours. 她经常跳舞跳上几个小时。
He will keep intruding. 他老是打扰别人。
11. guessing 推测、猜测：“must, should, may / might, can / could, would, ought to”
e.g. He may be very busy now.
This must be your pen. / This can"t be your pen.
It would be about ten when he left home.
What would she be doing there?
I thought he would have told you all about it.
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。
（A）情态动词表推测常用的三种句式：
1）在肯定句中一般用must (一定)，may（可能），might / could（也许，或许）。
以上情态动词的语气按程度是依次递减的。注意：might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。
e.g. He must / may / might know the answer to this question?
他一定 / 可能 / 也许知道这个问题的答案。
It is cold in the room. They must have turned off the heating.
屋里很冷，他们肯定把暖气关了。
2）否定句中用can"t / couldn"t (不可能), may not/might not (也许不会)。
e.g. It can"t / couldn"t be the headmaster. He has gone to America.
这不可能是校长，他去美国了。
He may not / might not know the scientist. 他也许不认识那位科学家。
3）疑问句中用can/could (能……?)。
e.g. Could he have finished the task? 他可能把任务完成了吗？
Can he be at home now? 他现在能在家吗？
（B）情态动词表推测常用的三种时态：
1）对将来情况的推测，用“情态动词 + 动词原形”。
e.g. She must / may / might / could arrive before 5. 5:00前她一定/可能/也许到。
She must/may/might/could walk miles and miles among the hills without meeting anyone.
她一定/可能/也许会在山里一连走好几英里而遇不到一个人。
2）对现在或一般情况的推测，用“情态动词 + be”，“情态动词 +be doing”或“情态动词 + 动词原形”。
e.g. He must / may / might / could be listening to the radio now.
他一定/可能/也许正在听收音机。
He can"t ( couldn"t ) / may ( might ) not be at home at this time.
这个时候他不可能/可能不在家。
How can (could) he be late for the opening ceremony ?
布什先生一向准时，这次开幕式他怎么可能迟到呢？
It"s seven o"clock. Jack should/ought to be here at any moment.
现在七点钟了，杰克理应随时到达。（推测）
3）对过去情况的推测用“情态动词 + have +过去分词”。
e.g. It must / may / might / could have rained last night. The ground is wet.
地湿了，昨晚肯定/可能/也许下雨了。
The door was locked. He can (could ) not / may ( might ) not have been at home.
门锁着，他不可能/可能不在家。
Can / Could he have gotten the book？ 难道他找到书了吗？
Note: 虚拟语气:
e.g. They would be killed if the car went over the cliff.
如果汽车翻在悬崖下, 他们就会丧命。
They would have been killed if the car had gone over the cliff.
如果汽车当时翻到悬崖下, 他们早就丧命了。
She should / ought to have attended your birthday party, but she had to look after her mother in hospital.
她本该出席你的生日晚会的，可是她得在医院照顾她妈妈。
Tom should not /ought not to have told me your secret, but he meant no harm.
汤姆本不该告诉我你的秘密，可是他并无恶意。
He may not have finished the work.
(虚拟语气部分 Subjunctive Mood：See Chapter 16, 34)
12. dare和need的两重性: 情态动词和实义动词
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：
e.g. You needn"t come so early.
“— Need I finish the work today?
— Yes, you must.”
“needn"t + 完成式” 表示本来不必做某事而实际上做了某事:
You needn"t have waited for me for long. 没有必要等了我这么久。
“-- Need I attend the meeting?
-- No, you need not have arrived so earlier.”
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。
e.g. How dare you say I"m unfair!
He daren"t speak English before such a crowd, dare he?
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?
3) dare和need也作实义动词，有时态、人称和数的变化。
肯定句：dare + to do
e.g. He needs to finish it this evening.
I dare to swim across this river.
否定句: do not dare (to) do
e.g. Tom didn"t dare to do it. 汤姆不敢做那件事。
He does not dare (to) answer.
Don"t you dare (to) touch it!
He doesn"t dare to tell the teacher what happened that day.
疑问句：Does Do … dare (to) do….? 疑问句中可省略 to
e.g. Does she dare (to) go alone? 她敢一个人去吗?
Do you dare to walk in the dark? 你敢黑夜走路吗？
里论外几-
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 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,主要有下列: can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would),have (to) ,had better. 情态动词还有一个很重要的用法，即情态动词表推测—— 情态动词表推测的用法小结 （一）情态动词表推测的三种句式 1.在肯定句中一般用must (一定)，may（可能），might /can, could（也许，或许）。 （1）He must/may/might know the answer to this question? 他一定/可能/也许知道这个问题的答案。 （2）It is cold in the room. They must have turned off the heating. 屋里很冷，他们肯定把暖气关了。 2.否定句中用can"t / couldn"t(不可能), may not/might not(可能不)。 （1）It can"t/couldn"t be the headmaster. He has gone to America. 这不可能是校长，他去美国了。 （2）He may not/might not know the scientist. 他也许不认识那位科学家。 3.疑问句中用can/could (能……?)。 （1）Could he have finished the task? 他可能把任务完成了吗？ （2）Can he be at home now? 他现在能在家吗？ 注：以上三种句式中情态动词的语气按程度都是依次递减的。Might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。 （二）情态动词表推测的三种时态 1.对将来情况的推测，用“情态动词 + 动词原形”。 （1）She must / may / might / could arrive before 5. 5:00前她一定/可能/也许到。 （2）She must/may/might/could walk miles and miles among the hills without meeting anyone. 她一定/可能/也许会在山里一连走好几英里而遇不到一个人。 2.对现在或一般情况的推测，用“情态动词 + be”，“情态动词 +be doing”或“情态动词 + 动词原形”。 （1）He must / may / might / could be listening to the radio now. 他一定/可能/也许正在听收音机。 （2）He can"t ( couldn"t ) / may ( might ) not be at home at this time. 这个时候他不可能/可能不在家。 （3）Mr. Bush is on time for everything .How can ( could ) he be late for the opening ceremony ? 布什先生一向准时，这次开幕式他怎么可能迟到呢？ 3.对过去情况的推测，用“情态动词 + have +过去分词”。 （1）It must / may / might / could have rained last night .The ground is wet. 地湿了，昨晚肯定/可能/也许下雨了。 （2）The door was locked. He can ( could ) not / may ( might ) not have been at home . 门锁着，他不可能/可能不在家。 （3）Can / Could he have gotten the book？ 难道他找到书了吗？ 注：情态动词 should /ought to表推测时，意为“想必会，理应……”但与“have +过去分词”连用时，则又可构成虚拟语气意为“本应该做某事却没做”。例如： （4）It"s seven o"clock. Jack should/ought to be here at any moment. 现在七点钟了，杰克理应随时到达。（推测） （5）She should / ought to have attended your birthday party, but she had to look after her mother in hospital. （虚拟） 她本该出席你的生日晚会的，可是她得在医院照顾她妈妈。 （6）Tom should not /ought not to have told me your secret, but he meant no harm. （虚拟） 汤姆本不该告诉我你的秘密，可是他并无恶意。
再也不做稀饭了-
can, could ,may ,might ,must ,need ,have to, ought to ,had better,would,
瑞瑞爱吃桃-
must
can
could
may
might
dare(高中才正式讲)
will
shall
should
need