英語(yǔ)的朋友們應(yīng)該知道情態(tài)動(dòng)詞吧? 情態(tài)動(dòng)詞(Modal verbs)本身有一定的詞義，表示語(yǔ)氣的單詞。但是不能獨(dú)立作謂語(yǔ)，只能和動(dòng)詞原形一起構(gòu)成謂語(yǔ)。情態(tài)動(dòng)詞用在行為動(dòng)詞前，表示說(shuō)話(huà)人對(duì)這一動(dòng)作或狀態(tài)的看法或主觀(guān)設(shè)想。今天來(lái)看看他們的用法吧。

情態(tài)動(dòng)詞雖然數(shù)量不多，但用途廣泛，主要有下列：can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would)。

因?yàn)榍閼B(tài)動(dòng)詞帶有某種的情緒性，比如dare就很強(qiáng)硬，比較負(fù)面，而may就比較的和善，為了避免在談話(huà)時(shí)把“討論”變成“攻擊”。

分類(lèi)

情態(tài)動(dòng)詞有四類(lèi)：

①只做情態(tài)動(dòng)詞：

must,can(could),may(might),ought to

②可做情態(tài)動(dòng)詞又可做實(shí)義動(dòng)詞：

need,dare

③可做情態(tài)動(dòng)詞又可做助動(dòng)詞：

shall(should),will(would)

④具有情態(tài)動(dòng)詞特征：

have(had) to,used to

位置

情態(tài)動(dòng)詞在句中放在謂語(yǔ)動(dòng)詞之前, 謂語(yǔ)動(dòng)詞前若有助動(dòng)詞,則在助動(dòng)詞之前,疑問(wèn)句中，情態(tài)動(dòng)詞則在主語(yǔ)之前。

I can see you. Come here.

我能看見(jiàn)你，過(guò)來(lái)吧。

He must have been away.

他一定走了。

What can I do for you?

我能幫你嗎?

How dare you treat us like that!

你怎能那樣對(duì)待我們!

特點(diǎn)

情態(tài)動(dòng)詞無(wú)人稱(chēng)和數(shù)的變化, 情態(tài)動(dòng)詞后面跟的動(dòng)詞需用原形,否定式構(gòu)成是在情態(tài)動(dòng)詞后面加 "not"。

個(gè)別情態(tài)動(dòng)詞有現(xiàn)在式和過(guò)去式兩種形式, 過(guò)去式用來(lái)表達(dá)更加客氣, 委婉的語(yǔ)氣, 時(shí)態(tài)性不強(qiáng), 可用于過(guò)去，現(xiàn)在或?qū)?lái)。情態(tài)動(dòng)詞屬非及物動(dòng)詞，故沒(méi)有被動(dòng)語(yǔ)態(tài)。情態(tài)動(dòng)詞沒(méi)有非謂語(yǔ)形式，即沒(méi)有不定式，分詞，等形式。

He could be here soon.

他很快就來(lái)。

We can t carry the heavy box.

我們搬不動(dòng)那箱子。

I m sorry I can t help you.

對(duì)不起，我?guī)筒簧夏恪?/p>

基本助動(dòng)詞與情態(tài)助動(dòng)詞最主要的區(qū)別之一是，基本助動(dòng)詞本身沒(méi)有詞義，而情態(tài)助動(dòng)詞則有自己的詞義，能表示說(shuō)話(huà)人對(duì)有關(guān)動(dòng)作或狀態(tài)的看法，或表示主觀(guān)設(shè)想：

What have you been doing since? (構(gòu)成完成進(jìn)行體，本身無(wú)詞義)

I am afraid I must be going. (一定要)

You may have read some account of the matter. (或許已經(jīng))

除此之外，情態(tài)助動(dòng)詞還有如下詞法和句法特征：

1) 除ought和used以外，其他情態(tài)動(dòng)詞后面只能接不帶to的不定式。如果我們把ought to和used to看做是固定詞組的話(huà)，那么，所有情態(tài)動(dòng)詞無(wú)一例外地只能接不帶to的不定式：

We used to grow beautiful roses.

I asked if he would come and repair my television set.

2) 情態(tài)助動(dòng)詞在限定動(dòng)詞詞組總是位居第一：

They need not have been punished so severely.

3) 情態(tài)助動(dòng)詞用于第三人稱(chēng)單數(shù)現(xiàn)在時(shí)的時(shí)候，沒(méi)有詞形變化，即其詞尾無(wú)-s形式：

She dare not say what she thinks.

4) 情態(tài)動(dòng)詞沒(méi)有非限定形式，即沒(méi)有不定式和分詞形式，也沒(méi)有相應(yīng)的動(dòng)名詞：

Still, she needn t have run away.

5) 情態(tài)助動(dòng)詞的“時(shí)”的形式并不是時(shí)間區(qū)別的主要標(biāo)志。在不少場(chǎng)合，情態(tài)助動(dòng)詞的現(xiàn)在時(shí)和過(guò)去時(shí)形式都可以表示現(xiàn)在、過(guò)去或?qū)?lái)時(shí)間：

Would you mind very much if I ask you to do something?

She told him he ought not to have done it.

6) 情態(tài)助動(dòng)詞之間是相互排斥的，即在一個(gè)限定動(dòng)詞詞組中只能出現(xiàn)一個(gè)情態(tài)助動(dòng)詞，但有時(shí)卻可以與have和be基本助動(dòng)詞連用：

You should have washed the wound.

Well, you shouldn t be reading a novel.

用法

首先它是動(dòng)詞，而且不同于行為動(dòng)詞，行為動(dòng)詞表示的是可以通過(guò)行為來(lái)表達(dá)的動(dòng)作(如寫(xiě)，讀，跑)，而情態(tài)動(dòng)詞只是表達(dá)的一種想法(如能，也許，敢)。

用法是：情態(tài)動(dòng)詞+行為動(dòng)詞原形

例句：I can read this sentence in English.

我能用英語(yǔ)讀這句話(huà)。

情態(tài)動(dòng)詞是一種本身有一定的詞義,表示說(shuō)話(huà)人的情緒,態(tài)度或語(yǔ)氣的動(dòng)詞,但不能單獨(dú)作謂語(yǔ),只能和其他動(dòng)詞原形構(gòu)成謂語(yǔ)。

We can be there on time tomorrow.

我們明天能按時(shí)去那兒。

May I have your name?

我能知道你的名字嗎?

Shall we begin now?

我們現(xiàn)在就開(kāi)始嗎?

You must obey the school rules.

你必須遵守校規(guī)。

功能

助動(dòng)詞(auxiliary)主要有兩類(lèi)：基本助動(dòng)詞(primary auxiliary)和情態(tài)助動(dòng)詞(modal auxiliary)。

基本助動(dòng)詞有三個(gè)：do, have和be;

情態(tài)助動(dòng)詞有十三個(gè)：may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to.

上述兩類(lèi)助動(dòng)詞的共同特征是，在協(xié)助主動(dòng)詞構(gòu)成限定動(dòng)詞詞組時(shí)，具有作用詞的功能：

1) 構(gòu)成否定式：

He didn t go and neither did she.

The meeting might not start until 5 o clock.

2) 構(gòu)成疑問(wèn)式或附加疑問(wèn)式：

Must you leave right now?

You have been learning French for 5 years, haven t you?

3) 構(gòu)成修辭倒裝：

Nowhere can he obtain any information about his sister.

Hardly had he arrived when she started complaining.

4) 代替限定動(dòng)詞詞組：

A: Who can solve this crossword puzzle?

B: Tom can.

A: Shall I write to him?

B: Yes, do.

用法要點(diǎn)

can, could

1) 表示能力(體力、知識(shí)、技能)。

Can you lift this heavy box?(體力)

Mary can speak three languages.(知識(shí))

Can you skate?(技能)

此時(shí)可用be able to代替。Can只有一般現(xiàn)在時(shí)和一般過(guò)去式;而be able to則有更多的時(shí)態(tài)。

I’ll not be able to come this afternoon.

當(dāng)表示“經(jīng)過(guò)努力才得以做成功某事”時(shí)應(yīng)用be able to，不能用Can。

如：He was able to go to the party yesterday evening in spite of the heavy rain.

2) 表示請(qǐng)求和允許。

Can I go now?

Yes, you can. / No, you can’t.

此時(shí)可與may互換。在疑問(wèn)句中還可用could,might代替，不是過(guò)去式，只是語(yǔ)氣更委婉，不能用于肯定句和答語(yǔ)中。

Could I come to see you tomorrow?

Yes, you can. ( No, I’m afraid not. )

3) 表示客觀(guān)可能性(客觀(guān)原因形成的能力)。

They’ve changed the timetable, so we can go by bus instead.

This hall can hold 500 people at least.

4) 表示推測(cè)(驚訝、懷疑、不相信的態(tài)度)，用于疑問(wèn)句、否定句和感嘆句中。

Can this be true?

This can’t be done by him.

How can this be true?

特別說(shuō)明：

(1) could用來(lái)表示請(qǐng)求時(shí)，語(yǔ)氣委婉，主要用于疑問(wèn)句，不能用于肯定句，答語(yǔ)應(yīng)用can(即：could不能用于現(xiàn)在時(shí)態(tài)的簡(jiǎn)略答語(yǔ)中)。

Could I use your dictionary?

Yes, you can.(否定回答可用：No, I’m afraid not.)

此時(shí)可與may互換。在疑問(wèn)句中還可用could,might代替，不是過(guò)去式，只是語(yǔ)氣更委婉，不能用于肯定句和答語(yǔ)中。

Could I come to see you tomorrow?

Yes, you can. ( No, I’m afraid not. )

(2) can和be able to辨析

can(could)和be able to都可以表示能力，意思上沒(méi)有區(qū)別。但can只有現(xiàn)在式和過(guò)去式，而be able to則有更多的形式。

如：

I’ve always wanted to able to speak fluent English.

Those bags look really heavy, are you sure you’ll be able to carry them on your own?

但是，表示在過(guò)去某時(shí)的某一場(chǎng)合經(jīng)過(guò)一番努力，終于做成了某事，通常不用could，而用was/were able to來(lái)表示。could：有潛能，但并未做到，這時(shí)was/were able to相當(dāng)于managed to do或succeed in doing。

如：

After the accident it was a long time before she was able to walk again.

The fire was very big, but most people were able to escape from the building.

I can sing many English songs.

我會(huì)唱許多英文歌曲。

We were able to return to our campsite before the heavy rain.

我們?cè)谙麓笥昵霸O(shè)法會(huì)到了野營(yíng)地。

He was able to swim across the river and escaped being caught.

他游到了河對(duì)岸，沒(méi)有被抓住。

在否定句中，can/could與be able t幾乎沒(méi)有什么差別，兩者可以互換。例如：

She wasn’t able to/couldn’t cook French dishes.

她不會(huì)做法國(guó)菜。

(3) 慣用形式“can not …too…”表示“無(wú)論怎么……也不(過(guò)分)”。

如：

You cannot be too careful.

你越小心越好。

慣用形式“can not but+ 不定式(不帶to)”表示“不得不，只好”。如：

I can not but admire her determination.

我不得不欽佩你的決心。

may, might

1) 表示請(qǐng)求和允許。might比 may語(yǔ)氣更委婉，而不是過(guò)去式。否定回答時(shí)可用can’t或mustn’t，表示“不可以，禁止”。

Might/ May I smoke in this room?

No, you mustn’t.

May/Might I take this book out of the room?

Yes, you can. (No, you can’t / mustn’t. )

用May I...?征徇對(duì)方許可時(shí)比較正式和客氣，而用Can I...?在口語(yǔ)中更常見(jiàn)。

2)用于祈使句，表示祝愿。

May you succeed!

3) 表示推測(cè)、可能性(不用于疑問(wèn)句)。

might不是過(guò)去式，它所表示的可能性比may小。

1.He may /might be very busy now.

2.Your mother may /might not know the truth.

must, have to

1) 表示必須、必要。

You must come in time.

在回答引出的問(wèn)句時(shí)，如果是否定的，不能用mustn t(禁止，不準(zhǔn))，而用needn’t, don’t have to(不必).

Must we hand in our exercise books today?

Yes, you must.

No, you don’t have to / you needn’t.

2) must是說(shuō)話(huà)人的主觀(guān)看法， 而have to則強(qiáng)調(diào)客觀(guān)需要。Must只有一般現(xiàn)在時(shí)， have to 有更多的時(shí)態(tài)形式。

1. He play isn’t interesting, I really must go now.

2. I had to work when I was your age.

3) 表示推測(cè)、可能性(只用于肯定的陳述句)

1. You’re Tom’s good friend, so you must know what he

likes best.

2. Your mother must be waiting for you now.

dare, need

1) dare作情態(tài)動(dòng)詞用時(shí), 常用于疑問(wèn)句、否定句和條件從句中, 過(guò)去式形式為dared。

1. How dare you say I’m unfair?

2. He daren’t speak English before such a crowd, dare he?

3. If we dared not go there that day， we couldn’t get the beautiful flowers.

2) need 作情態(tài)動(dòng)詞用時(shí), 常用于疑問(wèn)句、否定句。在肯定句中一般用must, have to, ought to, should代替。

1.You needn’t come so early.

2. Need I finish the work today?

Yes, you must. / No, you needn’t.

3) dare和 need作實(shí)義動(dòng)詞用時(shí)， 有人稱(chēng)、時(shí)態(tài)和數(shù)的變化。在肯定句中，dare后面常接帶to的不定式。在疑問(wèn)句和否定句中，dare后 面可接帶to或不帶to的不定式。而need后面只能接帶to的不定式。

1. I dare to swim across this river.

2. He doesn’t dare (to) answer.

3. He needs to finish his homework today.

shall, should

1) shall 用于第一人稱(chēng)，征求對(duì)方的意見(jiàn)。

What shall we do this evening?

2) shall 用于第二、三人稱(chēng)，表示說(shuō)話(huà)人給對(duì)方的命令、警告、允諾或威脅。

1. You shall fail if you don’t work hard.(警告)

2. He shall have the book when I finish it.(允諾)

3. He shall be punished.(威脅)

will, would

1) 表示請(qǐng)求、建議等，would更委婉。

Will / Would you pass me the ball, please?

2) 表示意志、愿望和決心。

1. I will never do that again.

2. They asked him if he would go abroad.

3) would表示過(guò)去反復(fù)發(fā)生的動(dòng)作或某種傾向。would表示過(guò)去習(xí)慣時(shí)比used to正式，且沒(méi)有“現(xiàn)已無(wú)此習(xí)慣”的含義。

1. During the vacation, he would visit me every other day.

2. The wound would not heal.

4) 表示估計(jì)和猜想。

It would be about ten o’clock when she left home.

特別說(shuō)明：would與used to辨析

would可用來(lái)表示過(guò)去反復(fù)出現(xiàn)的動(dòng)作，但不能表示過(guò)去存在的狀態(tài)，所以我們不能說(shuō)：“she would be a quiet girl.”

另外，would強(qiáng)調(diào)過(guò)去某種特定情況下的活動(dòng)，是完全過(guò)去的事情，同現(xiàn)在沒(méi)有聯(lián)系。而used to則著眼于過(guò)去和現(xiàn)在的對(duì)比，隱含現(xiàn)在已不存在，動(dòng)作或狀態(tài)都可表示。Would可以表示不規(guī)則的習(xí)慣，used to則不可。

如：

He used to be a naughty boy and cause trouble.

I used to get up at six in the morning.

Sometimes she would take a walk in the neighboring woods.

In those days, whenever I had difficulties, I would go to Mr. Chen for help.

should, ought to

1) should, ought to表示“應(yīng)該”，ought to表示義務(wù)或責(zé)任，比should語(yǔ)氣重。

1. I should help her because she is in trouble.

2. You ought to take care of the baby.

2) 表示勸告、建議和命令。should, ought to可通用，但在疑問(wèn)句中常用should。

1. You should / ought to go to class right away.

2. Should I open the window?

3) 表示推測(cè)，should , ought to (客觀(guān)推測(cè)), must(主觀(guān)推測(cè))。

1.He must be home by now. (斷定他已到家)

2.He ought to/should be home by now.(不太肯定)

3. This is where the oil must be.(直爽)

4. This is where the oil ought to/should be.(含蓄)

情態(tài)動(dòng)詞+不定式完成式(have done)

1) can / could + have done在肯定句中表示“本來(lái)可以做而實(shí)際上能做某事”，是虛擬語(yǔ)氣;在疑問(wèn)句或否定句中表示對(duì)過(guò)去行為的懷 疑或不肯定, 表示推測(cè)。

1. You could have done better, but you didn’t try your best.(虛擬語(yǔ)氣)

2. He can’t have been to that town.(推測(cè))

3. Can he have got the book?(推測(cè))

2) may / might +不定式完成式(have done)表示對(duì)過(guò)去行為的推測(cè)。不能用于疑問(wèn)句中，沒(méi)有虛擬語(yǔ)氣的用法。Might所表示的可能性比may小。

1. He may not have finished the work .

2. If we had taken the other road, we might have arrived earlier.

3)must +不定式完成式(have done)用于肯定句中，表示對(duì)過(guò)去行為的推測(cè)。意為“一定、想必”。其疑問(wèn)、否定形式用can，can’t代替。參看1) can / could + have done表示推測(cè)。

1. You must have seen the film Titanic.

2. He must have been to Shanghai.

4)should +不定式完成式(have done)用于肯定句中，表示對(duì)過(guò)去行為的推測(cè)。

He should have finished the work by now。

表示“本應(yīng)該做而實(shí)際上沒(méi)有做某事”，其否定式表示某種行為本不該發(fā)生卻發(fā)生了?？梢耘cought to +不定式完成式(have don e)互換。

1. You ought to / should have helped him. (but you didn’t.)

2. She shouldn’t have taken away my measuring tape, for I wanted to use it.

5) needn’t +不定式完成式(have done)表示“本來(lái)不必做而實(shí)際上做了某事”。

You needn’t have watered the flowers, for it is going to rain.

6) will +不定式完成式(have done)主要用于第二、三人稱(chēng)，表示對(duì)已完成的動(dòng)作或事態(tài)的推測(cè)。

He will have arrived by now.

情態(tài)動(dòng)詞表示猜測(cè)

肯定：must>should>could>may>might

否定：can’t>shouldn’t>couldn’t>may not>

表示要求，命令時(shí)，語(yǔ)氣由 should(應(yīng)該)、had better最好)、must(必須)漸強(qiáng)。

必須掌握情態(tài)動(dòng)詞表示推測(cè)語(yǔ)氣時(shí)的反意疑問(wèn)句。

例如：

The road is wet. It must have rained, hasn t it?

The road is wet. It must have rained last night, didn t it? (多了過(guò)去時(shí)的時(shí)間狀語(yǔ))

I met him on his way home. He can’t be in the library now, isn t he?

The coat is too close to the fire. It might get burnt, doesn t it?

大家都看明白了嗎?是不是對(duì)自己平時(shí)的學(xué)習(xí)有了新的認(rèn)識(shí)?如果你覺(jué)得自己的英語(yǔ)水平還不夠的話(huà)，一定要多多努力，上面的內(nèi)容只是英語(yǔ)中的一個(gè)小小的知識(shí)點(diǎn)。大家要從這個(gè)知識(shí)點(diǎn)入手，學(xué)習(xí)更多更好更優(yōu)質(zhì)內(nèi)容。