助动词

英语中助动词主要有三类：一是基本助动词，如have, do, be；二是半助动词, 如 be about to等；三是情态助动词，如may, must, need等。 基本助动词

助动词可表示动词时态和语态,构成疑问句和否定句,例如 “have, has, had”用来构成完成时态； “be, is, are, am, been, was, were, being” 构成被动语态 What do you do every day?

Betty has completed her work on time. Jason is writing a new book. A rat was caught by a cat.

构成疑问句附加语，如： Mr. Chen has not become a businessman, has he? Jason's lectures are clear and easy-to-understand, aren't they? 构成省略句，如：

The boss doesn't often come to the factory and when he does, it is generally on Sunday. 半助动词

在功能上介乎主动词和助动词之间的一类结构，称为半助动词。常见的半助动词有be about to, be apt to, be bound to, be due to, be going to, be liable to, be likely to, be obliged to, be supposed to, be willing to, have to, seem to, chance to, have got to, turn out to, tend to等。

它们可与主动词搭配构成复杂动词词组并表示情态意义，从而像是情态助动词；有时也可与助动词搭配 ,像是主动词，例如: I have to buy a new car. He seems to be disappointed. I don’t have to buy a new car.

He doesn’t seem to be disppointed. 情态动词

情态动词有can (could), may (might), dare (dared), shall (should), will (would) , must, need, ought to, used to. 一、情态动词+动词原形 Can

1).can, could 表示能力

①表示现在的能力,用can或be able to

As I hve got enough money, I can/am able to help her. ②表示将来的能力，可用can, 但更常用will/shall be able to I’ll be able to speak German in another two months.

③表示过去的能力，在肯定句中，could泛指过去的一般能力,做某件具体事情的能力常用was/were able to，即成功地做成了某件具体的事。 She could play the piano when she was only six. He was able to flee Europe before the war broke out. = He managed to flee Europe before the war broke out. 但以上区别仅就肯定句而言，在否定句中无此限制。 2）表示客观可能性和推测

Man cannot live without air. Can it be Tom?

3)Can/could表示请求和允许

Can I go now? Yes, you can. Could I come to see you tomorrow? Yes,you can. No,I am afraid not.

4)表示惊异，怀疑，不相信（主要用于否定， 疑问或感叹句） This can not be done by him. How can you be so careless! Can this be true? 5) can not help but do

I can not help but wonder what he is doing. 6). can not help doing can not help (to) do

7). can not (never, hardly) do …too… 越．．就越好；无论做．．都不过分 a. You can not be too careful in the exam. b. You can not praise him too highly. May

may表示“允许，可以”，相当于be allowed to You may go now.

May I use your computer?

may或might可和as well连用，表示“建议”，译为“还是……的为好” You may as well keep a certain distance from that mad man. You might as well go home now.

1） 表示允许或请求 当表示请求，允许时，might比may语气更委婉，否定答语要用must not,表示“不许可”、“不应该”、“不行”,或can not。 e.g. May I come in?

----Yes, you may\\can. ----No, you mustn‟t\\can‟t.

2).表示没有把握的推测. “也许”(用于肯定句或否定句中,不用于疑问句) 注意： might 表示推测时，不表示时态, 只是可能性比may 小。 e.g. a. He may be playing football. b. He might be at home。 3).may 放在句首，表示祝愿

e.g. a. May God bless you! b. May you succeed! = Wish you success! Must

must表示“必须”或“应当”、“一定” 在回答must引起的问题时，如果是否定的答复，不能用mustn‟t，而要用needn‟t或don‟t have to，因为mustn‟t是“一定不要”、“一定不能”的意思。 You must come to the classroom before eight. “Must we do it now?” “No, you needn‟t.” Must vs. have to

1) have to 加动词原形，表示“不得不”，“必须”，表示客观的需要，而must表示说话人主观上的看法，即主观上的必要

My brother was very ill, so I had to call the doctor in the middle of the night. (客观上需要做这件事)

b. He said that they must work hard. （主观上要做）

2) have to可用于多种时态，而must一般用于现在时，其过去时与将来时分别由had to与shall / will have to

3） 在否定结构中： don‟t have to表示“不必” mustn‟t表示 “禁止”

e.g. a. You don„t have to tell him about it. b. You mustn„t tell him about it.

4)must用于疑问句中，表责备，抱怨，常译为“偏要，硬要，干嘛” Tom, look at the time, must you play the piano at such a late hour? Should

should 表示“劝告”，“建议”或“义务”时，译作“应当”，或表示“预测”和“可能” He should take care of his parents as they are old enough not to live on themselves.

He should be there now.

should have done在虚拟语气中表示“责备或后悔

ought，只有一种形式，即ought后必须加to，然后跟接动词原形表示“有义务”或“必要”做某事，译为“应当，应该”

You ought not to make fun of him. He is not the one you laugh at but learn from. 1)用于第一人称疑问句中询问对方的意愿，但语气较委婉温和 What should we do now? 我们现在该怎么办？ 2)表示应该、必须，常与must 换用。

We should (must) master a foreign language at least. 3）表示推断，意思是“很可能，按理应该，估计” It is Monday, he should be at his office.

4) should have done 表示过去应该做而实际没有做

should not have done 表示过去不该做而实际做了． 5)表示惊异，意外等情绪，常译为“竟然”

It seems unfair that this should happen to me. 6)用于条件状语从句中“万一”

If it should rain tomorrow, we wouldn‟t go camping. Dare

dare作为情态动词时，主要用于疑问句和否定句，表示“敢”，后面跟不带to的动词不定式。如：How dare she do things like that to me? Dare you catch the mouse?

Dare也用作实义动词，其后的动词不定式可带to也可不带to，且dare有人称和数以及时态的变化。例如： I dare to jump down from the top of the wall. She doesn't dare (to) meet her teacher's eyes The little girl ____ the forest. A. didn‟t dare go to B. dared not go to C. dared not to go to D. dares not go to Need

need意为“需要”，既可作情态动词，也可作实义动词.

作情态动词无人称或数的变化， 后接动词原形，只能用于否定句和疑问句，如： You needn't worry.

Need you go before ten o‟clock?

need 作为行为动词有人称和数的变化， 后面可接名词、代词、动名词及带to 的动词不定式；可用于肯定句、疑问句和否定句中，如： She needs help.

I don‟t need to see the doctor. Do you need to go at once?

Need为行为动词时：1) need+sth/to do 2) 表被动 sth+need doing/to be done Will

will (would)决心,愿望。 would 为 will 的过去式, 可用于各种人称。 I'll do my best to catch up with them. It's hot. Will you open the windows? Would you like some coffee? 1）will表示经常性、习惯性、倾向性，would表示过去的习惯行为。含有“总是”，“习惯于”的意思。此时，would比used to 正式，且没有“现已无此习惯”之意． He will sit there hour after hour looking at the traffic go by. He would come to see me when he was in Beijing. 2）表示意志，决心或愿望。

Surely we will support all the people in the world in their struggle for peace.

He would not let me try it .

(3) 表示一种倾向，不受时限的客观过程，一种必然(普遍真理，自然倾向及事物品质)

Man will die without water. Oil will float on water.

(4) 物做主语时，will表示固有性质、功能，表示“因出毛病而不能…”, 相当于There is something wrong with sth. 的含义。 The bus won‟t start. 汽车开不动了。 The door won‟t open.

5)表示对对方的请求和建议，用于第二人称作主语的疑问句中，would的语气比will委碗,疑问句中一般用some, 而不是any。

Would/will you kindly tell me the way to the station? Would you like some cake? 6) would like = want to 想要 Would like to do

Would you like to go with me? 7) Would表示估计和猜想

I thought he would have told you all about it. What would he be doing there?

It would be about ten when he left home. Shall

1)用于第一、二、三人称征求听话人的的意见、意愿 What shall I wear on the journey? Shall you take a holiday this summer?

Shall my daughter do the shopping for you? 2)用于第二、三人称时表说话人的承诺

She shall get her share.

You shall have it back tomorrow.

3）用于二、三人称，表示说话人的决心，意思是“一定会，一定要”。 You shall obey my orders.

They shall do what I told them to. 4)用于第三人称，表示按条约、法令、规章等必须履行的义务，意义相当于must. Gambling in any form shall be banned. 二. 情态动词+动词完成式

must have ed分词表示推测过去某事“一定”发生了。其否定形式为：can‟t / couldn‟t have ed分词, 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.

may (might)+have+ed分词：用于肯定句和否定句，表示对已发生事情的不肯定的推测，相当于“可能，大概，”其中might较may 语气更弱，把握更小 She might have gone to see her doctor last week, but I am not sure.

Should (ought to)+have+ed分词：肯定句表示过去本应发生的事却没有发生；否定句表示已发生了本不该发生的事。前者可译为“本应，”后者为“本不该” You should have apologized to her for not soon replying to the letter.

You ought not to make fun of him. He is not the one you laugh at but learn from.

Can /could have done 表示假设，与过去的事实相反。推测过去某动作“很可能”发生了, can和could一般用于否定句和疑问句，could的语气较can弱。 例如： He could have been very rich, but he cared for no money at all. He can't have finished the work so soon.

needn‟t+have+ed分词：表示对过去不必做的事情却做了，可译为“其实不必” You needn‟t have waken me up; I don‟t have to go to work today.

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.”

三. 情态动词+动词进行式

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. 带to 的情态动词

带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to (=must),

be able to为六个,它们的疑问、否定形式应予以注 意：

Do they have to pay their bill before the end of the month? She didn‟t use/used not to play tennis before she was fourteen. You ought not to have told her all about it. Ought he to see a heart specialist at once?

情态动词的回答方式

问句 肯定回答 否定回答 Need you…?Yes, I must. No,I needn„t

Must you…?Yes, I must. No, I needn‟t. /don‟t have to. May I …? Yes, of course. No, you mustn‟t. Could I…? Yes, you can. No, you can‟t.

3. 表示推测的用法各种时态

can, could, may, might, must 皆可表示推测，其用法如下： 1）情态动词+动词原形。

表示对现在或将来的情况的推测，此时动词 通常为系动词。 I don't know where she is, she may be in Wuhan. 2）情态动词+动词现在进行时。

表示对现在正在进行的情况进行推测。

At this moment, our teacher must be correcting our exam papers. 3）情态动词+动词完成时。 表示对过去情况的推测。

The road is wet. It must have rained last night. 4）情态动词+动词的现在完成进行时。 表示对过去正在发生事情的推测。

She may have been expressing her true feelings at that moment.