知识讲解 情态动词(I)

情态动词（Ⅰ）

编稿: 审稿：梁晓

概念引入

The classroom can seat thirty students. 这教室能坐三十位学生。

You must obey the school rules.你必须遵守校规。

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。

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。

语法讲解

【高清课堂：356516情态动词情态动词】

概念：在动词(一般动词)之前形成动词的否定,疑问,时态,语态,语气或表示特殊意义的动词叫做助动词,其中具有感情色彩一些助动词叫做情态动词。

分类: be动词, have, do；

shall, should, will would, can, could, may, might, must, ought, need, dare, used和had better. shall

←shall在纯表示将来的陈述句中只用于第一人称。

←在问句中征求对方的意见和指示的时候常用于第一、三人称。

?Shall I post your letter for you?

?Shall we carry your baggage?

?Henry is waiting outside. Shall he come in?

用于第二、三人称，表示说话人的许诺、命令、警告、威胁等。

?Tell Jerry that he shall get a gift if he is nice.

?You shall be punished for what you’ve done.

should

←构成过去将来时作为shall的过去时。

He asked me whether I should be free tonight.

←表示主语的义务或责任。

●You shouldn’t eat between meals, for it will make you fat.

←表示很大的可能性，常译为“按道理说应该”。

●There should be a double “m” in the word swimming.

情态动词是一种本身有一定的词义，但要与动词原形及其被动语态一起使用，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。

can和could (could为can的过去式) 的基本用法

(1)表示能力，如：

He can speak English better than you.

can和be able to都可表示能力，两者在意思上没有什么区别。但是can只能有现在式和过去式，而be able to则有更多的形式，可位于情态动词之后或表达过去成功地做了某事。如：He will be able to do the work better.

He was able to finish the work on time.

(2) 表示客观的可能性

Accidents can happen to any drunken driver.

According to the radio, it could rain this afternoon.

(3)表示“许可”时can可以和may换用，如：

You can (may) go home now.如果要表示语气婉转，可用could代替can，这时could不再是can 的过去式，注意回答时不能用could。如：

----Could you come again tomorrow?

----Yes, I can./ No, I can’t.

(3) 在疑问句和否定句中表示怀疑、惊奇、不相信的态度。如：

Can this green bike be Liu Dong's?

How can you believe such a liar like him?

(4) 用于肯定句，表示一时的情况，意为：有时候会。如：

It can be very hot here in summer.

Tom is a clever boy, but he can be dull sometimes.

may和might (might为may的过去式)的基本用法

(1)表示允许或许可，否定用mustn’t, 表禁止。如：

---- May we swim in this lake?

---- No, you mustn't. It's too dangerous.

肯定可以用比较婉转的说法进行回答。如：

---- May I use this dictionary?

---- Yes, please. /---- Certainly. / Yes, you can.

(2)在表示请求、许可时，用might比may 语气更婉转些, 如：

May I have a look at your new computer?

May I…?在文体上较正式，较客气，日常口语中常用Can I…?

(3)may或might都可以表示可能性，表示"或许"、"可能"之意，如果用might表示可能性，则语气更加不肯定，如：Theymay (might) be in the library now .

He is absent. He may/ might be ill.

(4)May 用于祈使句，表示祝愿。如：

May you have a happy life.

May you succeed.

比较wish you a happy new year. Wish you success.

must的基本用法

(1)must表示“必须”、“应该”之意，语气比should, ought to强烈，其否定式must not，缩写形式为mustn‘t，表示“不准”、或“禁止”之意，如：

We must study hard and make progress every day.

You mustn't touch the fire.

(2)对以must提出的疑问句，如作否定回答时，要用needn‘t或用don’t (doesn‘t) have to (不必)来回答，而不用mustn’t，因为mustn‘t表示的是“禁止”或“不许可”之意，如：

---- Must we finish the work tomorrow?

---- No, you needn't (don't have to), but you must finishit in three days.

(3) must可以表示推测，表示“一定”或“必定”之意，只用于肯定句中。如：

---- Whose new bike can it be?

---- It must be Liu Dong's. I know his father has just bought him a new one.

You must be ill. I can see it from your face.

have to 的基本用法

(1)have to和must的意义相近，只是must侧重表示说话人的主观看法，而have to 则表示

客观需要，如：

I must study hard.

You have to hand in your compositions before next Monday.

(2)have to 有人称、数和时态的变化,否定式要用助动词，don’t have to如：

They had to speed up, for the weather turned terrible.

He has to stay at home because of illness

should的基本用法

(1)should表示“建议”或“劝告”，有“应该”之意，可与ought to 互换。如：

You should learn from each other.

You should/ ought to go and see Mary some time.

(2）表示推测，译作：很可能，该，是说话人对客观事物的真实性做出较大可能性的判断。如：

It’s already 10. She promised to come by 10. She should be here at any moment.

(3) why/how + should 表示“竟然”，含意外、惊异等语气。

Why should you be so late today?

I don’t understand why you should think that I did it.

(4)should后接完成式表示过去没有做到本来应该做的事情，或是做了本来不应该做的事情。如：

You should have given him more help.

You shouldn’t have left home without saying a word.

(5) 表示万一，用于if 从句

Ask Tom to ring me up if you should see him.

will的基本用法

(1) 可以表示“意志”或“决心”，如：

I have told him again and again to stop smoking, but he will not listen.

——Can someone help me? ——I will.

(2) 请求或询问对方的意愿，如：

Will you please tell me how to get to the Capital Gymnasium?

Will you open the window?

(3)表示一种习惯性的动作，有“总是”或“惯于”之意，will 指现在，would 指过去。如：Every morning he will have a walk along this river.

would的基本用法

(1)would作为will的过去式，可用于各人称，表示过去时间的"意志"或"决心"，如：He promised he would never smoke again.

(2)在疑问句中，用于第二人称，表示说话人向对方提出请求或许问对方的意愿时，比用will 的气更加婉转，如：Would you like some more coffee?

(3)在日常生活中，学用"I wou ld like to…"表示"我想要"或"我愿意"之意，以使语气婉转，如：

I would like to do Ex.2 first.

(4)would可以表示过去的习惯动作，比used to正式，并没有"现已无此习惯"的含义。如：Last year our English teacher would sometimes tell us stories in English after class. / During the vacation he would visit me every week.

(5)表料想或猜想，如：It would be about ten when he left home./ What would she be doing there?/

I thought he would have told you about it.

shall的基本用法

(1)在疑问句中，shall用于第一、三人称，表示说话人的征询对方意见或请求指示，如：Shall

I open the door?

(2)shall用作情态动词时，用于第二、三人称，表示说活人的意愿，可表示"命令"、"警告"、"强制"、"威胁"或"允诺"等意，如：He shall go first, whether he wants to or not.

need的基本用法

(1)need作情态动词用时，主要用于否定句和疑问句中，如：He needn't worry about us now.

(2)need也可作为行为动词用，可用于肯定句、否定句和疑问句中，其后可接名词、代词、动名词或带to 的动词不定式为其宾语。如：You need to practise reading aloud every day. (3)needn't后接完成式可以表示过去做了一件本来不必要做的事情，如：---- Did you answer the letter yesterday? ---- Yes, I did. ---- But you needn't have answered it.

dare的基本用法

(l)dare (dared为其过去式) 作情态动词用时，主要用于否定句，疑问句和条件从句中，如：Dare he break the traffic regulations again?

You will be punished if you dare do such a thing.

(2)在现代英语中dare常用作行为动词，其变化与一般行为动词相同，如：She dares to stay at home alone at night.