情态动词英语语法知识精讲
情态动词(modal verb)本身有词义，表示说话人的语气或情态，但词义不完全，不能单独用作谓语动词，一般只能和动词原形一起构成谓语动词。小编在这里整理了相关资料，希望能帮助到您。
情态动词概述
特征
1)情态动词(modal verb)本身有词义，表示说话人的语气或情态，但词义不完全，不能单独用作谓语动词，一般只能和动词原形一起构成谓语动词。
2)情态动词所表示的情态有：命令、允诺、请求、拒绝、愿望、愿意、义务、必要、可能、能力、敢于、需要等。
3)情态动词(ought除外)和助动词shall，will，should，would一样，后面的动词不定式一般皆不带。
形式变化
1)没有人称和数的变化，第三人称单数的现在时也无变化。如：
I can We can
You can You can
He
They can
She can
It
2)有些情态动词有过去式，有少数过去式和它的原形相同。
a)有过去式的情态动词有：
may -- would
can ―― could
may―― night
shall -- should
have to -- had to
b)过去式不变的情态动词有：
must - must (或had to)
ought to - ought to
need---need
dare - dare(亦可用dared)
3)大多数情态动词后面可用动词的进行式、完成式和被动形式，如：can(may，must)be doing，can(may，must) have done，can(may，must)be done等。
否定式
情态动词和助动词一样，后面可直接跟否定词not。现将情态动词的否定式及其否定式的简略式(简略式用于口语中)列举如下：
shall not--shan't [FB:nt]
will not---won't [wEunt]
can not-can't [kB:nt]
must not-mustn't [5mQsnt]
should not-- shouldn't
would not-- wouldn't
could not-- couldn't
dare not- daren't [dZEnt]
need not-- needn't
在疑问句中的用法
情态动词在疑问句中的用法和助动词相同。如：
May I ask you a question? 我可以问你一个问题吗?
Can you let me use your dictionary for a minute? 你能把字典借我用一会儿吗?
Would you like to visit the heavy machinery plant? 你想参观重型机器厂吗?
注意have to在疑问句中的位置。如：
Do you have to go out today? 你今天一定得出去吗?
Does he have to finish the work tomorrow? 他明天非做完这项工作不可吗?
情态动词--can, could
can和could
can的词义
表示体力或脑力方面的"能力"或客观上的"可能"。如：
Can you ride a bike? Yes，I can.你能骑自行车吗?是的，我能骑。
Can Mr. Smith use chopsticks? No，he can't . 史密斯先生会用筷子吗?不，他不会。
Most women here can read and write now.这里的多数妇女都能识字，也会写字。
In China even barren mountains can be turned into fertile fields. 在中国，荒山也能变成良田。
can用在否定句和疑问句中时
在这种句子中，can常可意谓"可能"，表示猜测和推理。如：
It surely can't be six o'clock already? 不可能已经六点钟了吧?
You can't be hungry so soon，Tom. You've just had lunch. 顿姆，你不可能饿得这么快，你刚吃过午饭。
She cannot be so careless. 她不可能这么粗心。
Where can he be? 他会在什么地方呢?
What can he mean? 他会是什么意思呢?
It surely can't be six o'clock already? 不可能已经是六点钟了吧?
[注一] can加动词的进行时态，也可表示"可能"。如：
What can he be doing all this time? 他一直会是在干什么呢?
She cannot be playing ping-pong now.她现在不可能在打乒乓球。
[注二] 在日常会话中，can可代替may表示"允许"，may比较正式，如：
You can drop in any time. 你随时都可以来串门。
Can I use your basin? of course，you can.我可以用你的脸盆吗?--当然可以。
You can have my seat，I'm going now.我要走了，你坐我的座位吧。
Could
could是Call的过去式，表示与过去有关的1)能力和2)可能(在否定和疑问句中)。如：
1)We were sure that he could do the work. 我们肯定他能做这工作。
He was a farmhand. He could not afford to send his son to school. 他是个雇农，他供不起儿子上学。
2)At that time we thought the Story could not be true.那时我们以为所说的事不可能是真的。
[注] could可代替can表示现在，但语气较为婉转。如：
could you wait half an hour?请你等半个小时好吗?
could you please ring up again at six? 六点钟请你再来电话好吗?
could we visit a kindergarten? I've been wanting to see one ever since I came to China.我们可以访问一个幼儿园吗?我自从到中国来以后，一直想看一所幼儿园。
[注二]表示过去的能力并已完成一具体动作时须用were (was) able (to)，不可用could。如：
I am glad we were able to catch the train. 我很高兴我们能赶上火车。但如未完成一具体动作，则可用could not。如：
I am sorry we couldn't (或weren't able to) catch the train.我很遗憾我们没有能赶上火车。
can的形式
can只有现在式can和过去式could两种形式，能表示现在一般和过去一般两种时态，有时也能表示将来。所有其他时态(包括将来)须用be able加动词不定式来表示。如：
With their help, we shall be able to finish the work in a few days. 有他们的协助，我们将会在几天之内完成这项工作。
They have not been able to come to Boston. 他们没有能到波斯顿来。
Mr. Johnson rang up just now to Say that he won't be able to come over this evening.约翰逊先生刚来电话，说今天晚上他来不了。
can，could用于否定或疑问句中
can (could)用于否定或疑问句中后面跟动词原形的完成式时，表示对过去发生事件的"可能性"。而could较can更加表示说话人的"不肯定的"语气。如：
Can he have left already? 他会是走了吗?
Could she have forgotten my address? 她会把我的地址忘记了吗?
It couldn't have been henry. He has gone to the factory. 不可能是亨利，他已经去工厂了。
Surely she can not have arrived so early. 他当然不可能这么早到这里的。
[注] could加动词的完成式时，有时表示"过去可能完成但事实上并没有实现的动作"。如：
You could have done the work better.你本来可以做得更好些。(事实上你做得不那么好)
You could have got the early train.你本来可以搭上早班火车的。(事实上没搭上)
情态动词--must
must
must的词义
must表示"必须"或"应当"。如：
I must leave at 9:00我必须在九点钟离开这里。
Soldiers must obey orders.士兵必须服从命令。
You must get to the stallion before three o'clock. 你必须在三点钟以前到达车站。
You must come earlier tomorrow.你明天得早点来。
must的否定式
must的否定形式must not表示"不应该"或
"不许可"，语气比较强烈。如：
We mustn't waste our time. 我们不应该浪费我们的时间。
Passengers must not walk across the railway line.旅客不要横穿铁路。
You mustn't miss that modern ballet，It is extremely good. 你可不要错过这个现代芭蕾舞剧，它好极了。
One must not divorce oneself from the masses.不应该脱离群众。
[注]说"不必"须用need not。如：
Must we hand in our exercises today? -No，You needn't.我们必须今天交练习吗? --不，不必今天交。
must也可表示过去
must只有现在式，通常用以表示现在，但有时也可以表示过去(多用在间接引语中)。如：
He told us we must all be ready by nine.他告诉我们在九点钟以前都得准备好。
It was too late to go back，we must go on.太晚了，回不去了，我们只有继续往前走。
[注] have to (必须)则可以表示各种时间。如：
I am afraid You will have to wait a while.我看你得等一会儿。
At every step I had to pull my legs out of the snow.我每走一步都得将双腿从雪中拔出来。
must也可表示说话人对事物的推测
但比may肯定得多，相当于汉语的"一定"或"准是"。如：
He must be in the library now. 他现在准是在图书馆。
The old man must be over seventy now.那老人准有七十多岁了。
She must know how to do farm work. 她一定懂得怎样干农活。
You ate very little at breakfast today. You must be hungry now.
你今天早餐吃得很少，现在一定饿了。
[注] must加动词原形的进行式，也可表示对现在发生的动作的推测，有"一定"、"准是"的意思。如：
She must be working on the experimental plot.她现在一定在试验田里工作。
must加动词原形的完成式
说明对过去事物的推测，表示"一定"或"准是"的意思。如：
I mailed the letter two weeks ago. She must have received it.
我是两星期以前发的信，她一定已经收到了。
She must have studied English before. 她以前一定学过英语。
How did you know about it? Somebody must have told you. 你怎么知道这事的?一定有人告诉你了。
情态动词--may, might
may和might
may表示"允许"或"请求"
May I come in? -Yes，do. 我可以进来吗?--请进。
May I borrow you raincoat? 我可以借用你的雨衣吗?
You may go now. 你现在可以走了。
You may ring us up any time during office hours.在办公时间你可以随时给我们打电话。
[注] may表示"允许"的否定形式是must not(不应该，不许可)。如：
May I take this book out of the reading-room? -No，you mustn't. 我可以把这本书拿出阅览室吗? --不行。
may还可表示说话人的猜测，认为某一事情"或许"或"可能"发生
We may call on you this evening.我们也许今天晚上来看你。
She may not go to the concert tonight.今晚她可能不去听音乐会了。
The news may or may not be true. 消息也许是真的，也许不是真的。
[注] may用在感叹句中可表示祝愿，愿望如：
May you succeed.祝你成功。
May you have a pleasant journey.一路平安。
might为may的过去式
The speaker said we might ask him any question.作报告的人说我们可以向他提任何问题。
He said he might go to the Palace Museum on Sunday. 他说他星期天可能去参观故宫博物院。
[注一]night也可代替may，表示现在，但语气较为婉转客气或更加不肯定。如：
He night not come today.今天他也许不来了。
Might I make a suggestion? 我可以提个建议吗?
[注二]might用来表示现在时，还可表示"规劝"，如：
You might，pay more attention to spoken English.你要更多地注意英语口语。
You might shut the windows. The wind is blowing so hard outside.关上窗户吧。外面风很大。
may (might)后加动词的完成式
表示对过去的推测，认为某一事情在过去"可能"发生。这里may和might都指过去，不过might较为含蓄委婉或更加不肯定(常用于肯定结构)。如：
Nick may (might) have gone to the library.尼克可能到图书馆去了。
Our manager may (might) have gone to Harbin last weekend.
我们的经理上周末可能已经去哈尔滨了。
She may (might) have missed the plane.她也许没赶上飞机。
[注一] may和might常用在so that和in order that所引导的目的状语从句中(现在英语中还经常用can)。如：
Write is in simple language in order that everybody may understand it. 为了大家都看得懂，你要用简明的文字写。
He died，so that others night 1iye.他为了别人而牺牲了。
[注三] might加动词的完成式，可说明某一事情在过去没有实现并含有"劝告"甚至"责备"的意思。如：
You might have told me earlier.你本来可以早点告诉我的。
You might have been more careful.你本来可以多加小心。
情态动词--have to
have to
have to加动词原形
表示"不得不"、"必须"的概念。它比must更含有"客观条件使得必须如此做"的意思，并有较多的时态。如：
Mr. Johnson has to work very hard to earn a living.约翰逊先生为了谋生不得不拼命干活。
I had to leave the party early last night. I wasn't very well.昨晚我只得早点离开晚会，我不大舒服。
We will have to get up very early tomorrow.我们明天必须起得很早。
I shall have to go to the clinic today for my bad cough.我咳嗽得厉害，今天必须去诊疗所看看。
[注]口语中的I have got to，you have got to等：I have to，you have to. Have I got to?和Do I have to?这两种疑问形式均可用。
[英语语法手册]情态动词--shall
shall
shall作为情态动词用于第二、三人称
可表示说话人给对方的"命令"、"警告"、"允诺"、"威胁"等概念。如：
You shall do it，whether you want to or not. 不管你愿意不愿意，你必须做这项工作。(命令)
You shall have the book as soon as I finish it.这本书我一看完就给你。(允诺)
You shall pay for it.你一定会受到惩罚的。(威胁)
在疑问句中，情态动词shall用于第一、三人称
表示说话人征求对方的意见或向对方请示。如：
What shall I do now? 我现在该做什么?
Shall we go for a walk? 我们去散步好吗?
Shall he come tomorrow? 你要他明天来吗?
情态动词--should
should
情态动词Should表示"劝告"、 "建议 "时
这时should常译作 "应当"。如：
We Should learn about the computer and make full use of it.我们应该了解计算机并加以充分利用。
You should listen to the doctor's advice.你应当听大夫的话。
You should study the article care fully. 你应当细，心学习这篇文章。
should还可以表示 "预测"、"可能"
They should be here by now.他们现在可能到了。
The reference book should be in the reading-room.这本参考书可能在阅览室里。
should有时表示说话人的感情如惊奇、愤怒、失望等
Why should I go? 我干吗要去?(不满)
I am sorry that he Should be so obstinate.我很遗憾，他竟这样固执。(失望)
It's strange that it should be so hot today.很怪，今天怎么这么热。(惊奇)
should后跟动词的完成式时
这时句子指的是过去的事情。如果是肯定句，常说明某件事本应完成而未完成;如果是否定句，表示发生了不应当发生的事情.如：
You should have stopped at in red light. 你见了红灯本应该停车。
You Should not have gone back to work without the doctor's permission.你不应当未经医生许可就回去工作。
He Should have come earlier. 他应早一点来。
情态动词--will
Will
情态动词Will
可用于各人称，表示 "意志"、"意愿"、"决心"、"允诺"等。如：
I will try. 我愿一试。
I will do my best. 我一定尽力而为。
We will never do it again. 我们永远不会再做此事了。
Which will you fake?你要哪一个?
Who will go with me? 谁愿和我一同去?
will在疑问句中用子第二人称时
这时句子表示说话人向对方提出请求或询问。如：
Will you please explain the sentence once more?请你再把这个句子解释一遍好吗?
Will you have western food or Chinese food，Mr. Smith? 史密斯先生，你吃西餐还是中餐?
Will you pass me the butter? 请你把黄油递给我好吗?
注意下面句中的won't亦表请求：
Won't you come in ?请进来好吗?
[注一] 在条件状语从句中须用现在一般时表将来，但当will用作情态动词表意愿时，则亦可用于条件状语从句，如I'll be glad if you will come.(你如愿来，我将会很高兴)。
[注二]will在下面句子中 = I suppose(我猜想)或probably(大概)。如：
This will be the room you are looking for. 这大概就是你要找的那个房间。
You will remember the story I told you the other day.你们大概还记得我那天给你们讲的那个故事。
[注三]will有时表示一种习惯动作或状态。如：
Water will boil at 100 degrees Centigrade.水总是在摄氏100度煮沸。
Boys will be boys.男孩子总是男孩子。
情态动词--would
Would
是will的过去式，可用于各人称，表示过去时间的"意志"、"愿望"和 "决心"等。如：
He declared that he would do everything to help us. 他说要尽一切可能来帮助我们。
I told peter that I would go along wit him.我告诉彼得我要跟他一块去。
All in e doctors and nurses told Dr. Bethune not to give his own blood to the wounded, but he wouldn't listen.和护士劝白求恩大夫不要把自己的血输给伤员，但是他不听。
would用来表示现在时间时
这时would不论是表达说话人本身的意志或向对方提出请求，均较will婉转。如：
Would you tell us something about yourself? 请跟我们谈谈你自己好吗?
Would you like to have a glass of wine? 你要喝杯酒吗?
Would you please tell me the way to the nearest bus-stop? 请告诉我去最近的公共汽车站怎么走好吗?
Would you mind helping me with my packing? 请你帮我打打行李好吗?
[注]在日常会话中，I would like to和I should like to都可以说，I would like的简略式为I'd like。如：
I should (would) like to have a look at the new television set.我想看看这架新电视机。
I'd like to borrow a copy of Alice in Wonderland.我要借一本《爱丽丝漫游奇境记》。
Would还可以表示过去习惯发生的动作
I found that retired persons would often go to the park to play chess.我发现退休的人经常到公园里下棋。
When he had a problem to solve，he would work at it until he found an answer.当他有个问题要解决时，他总是想办法一直到找到答案为止。
情态动词--ought
ought
ought只有一种形式，后面须跟带to的动词不定式。Ought表示"有义务或必要"做某件事，还可表示"劝告"。如：.
You ought to follow the old man's advice.你应当听那位老人的话。
You oughtn't to smoke so much.你不应当抽烟太多。
You ought to go to the clinic at once. You don't look well.你脸色不好，应该马上到医务室去。
[注]ought表示"应该"，语气比should 强。
ought后加动词不定式的完成式时
指过去的动作。如用肯定形式(ought to have done)，表示某一件事该做而未做，相当于should have done。如用否定形式(ought not to have done)，则表示一件不该做的事情发生了，相当于should not have done。如：
He ought to have done the exercise more carefully.这个练习他应当作得更细心一些。
I ought to have returned these books to the library last week. 我上星期就应当把这些书还给图书馆。
You ought not to have been so rude.你不该这样粗鲁。
You ought not to have taken his skates without asking him.你不该没有得到他的许可就把他的冰鞋拿走。
情态动词--dare
dare (敢)
的用法和其他动词有所不同。dare用于否定句或疑问句中时，其用法和其他情态动词一样，即dare本身无变化，后面所跟的动词不定式不带to。如：
They dare not tell the truth.他们不敢说真话。
Dare he admit his mistake? 他敢于承认错误吗?
He dared say no more。他不敢再说了。
但是dare用在肯定结构中时，后面的动词不定式可加to。如：
Young people should dare to think，dare to speak and dare to act.青年人要敢想、敢说、敢干。
[注一]在否定句或疑问句中，dare也可用作实义动词，用助动词do来帮助，后面的动词不定式可带to。如：
Do they dare to do it? 他们敢做这事吗?
The enemy did not dare to come out after dark.敌人夜间不敢出来。
[注二]注意下面将两种不同动词揉合在一起的说法。如：
I didn't dale come.我不敢来。
Who dares stop me? 谁敢阻拦我?
[英语语法手册]情态动词--need
need(需要)
的用法与dare几乎完全相同。即在否定句或疑问句中，和其他情态动词一样，本身无变化，后面用不带to的动词不定式;在肯定句中时，和实义动词一样，后面的动词不定式要带to，第三人称单数现在一般时加-s，并有时态的变化。如：
Need we return the magazines today?我们今天需要把杂志还回去吗?
Every member needs to pay only a little money a year to get medical care.每个成员每年只需缴一点钱就可以得到医疗。
You need not write down your translation. You may do it orally. 你们不必写下这个翻译练习，口头做就行了。
[注]与dare一样，在否定句或疑问句里，need也可和实义动词相同，用助动词to do来帮助，后面的动词不定式必须带to。如：
Do they need to take any tools with them? -No., they don't need to.他们需要带工具吗? --不需要。
He did not need to go there early that day. 那天他不必早去。
need后面有名词作宾语时
完全用作实义动词，表示"需要"或"缺乏"某件事物。这时，它的变化和一般实义动词完全相同。如：
I need a dictionary.我需要字典。
You need a hair-cut. 你该理发了。
Do you need a fountain-pen? 你需要一支自来水笔吗?
I don't need a new jacket. 我不需要一件新茄克衫。
Mary looks tried，she needs a rest. 玛丽看上去累了，需要休息。
Needn't后加动词不定式(不带to)的完成式时
指过去已做了但勿须做的动作。如：
You needn't have watered the vegetables，as it is going to rain.你满可以不必浇菜，天要下雨了。
You needn't have brought your umbrella. We are going by taxi你满可以不必带伞，我们要坐出租汽车去。
[注一]注意didn't have to和didn't nee to则常表示过去未做也勿须做的动作。如：
I didn't have to interpret it for her，for she knows Chinese.我勿须为她翻译，她懂汉语。
I didn't need to take a taxi; it is only five minutes walk to the station.到车站只须走五分钟，我不需要坐出租汽车。
[注二] used to和had better也可看作是情态动词。情态动词used to表示过去的习惯，但现在已无此习惯(would表过去习惯时则无此含义)。如：
When I was young，I used to play football.我小时常踢足球。
He didn't use to come. (或用usedn't to)他过去不常来。
Did he used to come? (亦可说used he to...?)他过去常来吗?had better表可取，意为"应该"或"最好"。如：
We had better go now. 我们最好走吧。
You'd better stop now.你现在应该停下来。(对长辈不可用had better)
Hadn't we better go now? 我们现在走不好吗?(had better一般不用于肯定疑问句)
