情态动词优秀（原创精品）XX年普通高考英语科语法知识网络专题08?情态动词和虚拟语气i.情态动词基本用法情态动词用?法否定式疑问式简答式can能力（体力，智下面是小编为大家整理的情态动词优秀⑥篇,供大家参考。
（原创精品）XX年普通高考英语科语法知识网络
专题08? 情态动词和虚拟语气i.情态动词基本用法
情态动词
用? 法
否定式
疑问式
简答式
can能力（体力，智力，技能）允许或许可（口语中常用）可能性（表猜测，用于否定句或疑问句中）can not / cannot /can’t docan…do…?yes,…,…can’t.
couldcouldn’t do
may可以（问句中表示请求）可能，或许（表推测）祝愿（用于倒装句中）may not do may…do…?
yes,…may. no,…mustn’t/can’t.
mightmight not domight…do…?yes,…mightno,…might not.
must必须，应该（表主观要求）肯定，想必（肯定句中表推测）must not/mustn’t domust…do…????? to.yes,…,…needn’t/don’t have
have to只好，不得不（客观的必须，有时态和人称的变化）don’t have to dodo…have to do…?yes,…do.? no,…don’t.
ought to应当（表示义务责任，口语中多用should）ought not to/oughtn’t to doought…to do…?yes,…ought. no,…oughtn’t.
shall用于一三人称征求对方意见用于二三人称表示许诺、命令、警告、威胁等shall not/shan’t doshall…do…?yes,…shall.? no,…shan’t.
should应当，应该（表义务责任）本该（含有责备意味）should not/shouldn’t doshould…do…?
will意愿，决心请求，建议，用在问句中would比较委婉will not/won’t dowill/would…do…?yes,…will.? no,…won’t.
wouldwould not/wouldn’t do
dare敢（常用于否定句和疑问句中）dare not/daren’t dodare…do…?yes,…,…daren’t.
need需要，必须（常用于否定句和疑问句中）need not/needn’t doneed…do…?yes,…must. no,…needn’t.
used to过去常常（现在已不再）used not/usedn’t/usen’t to dodidn’t use to doused…to do…?did…use to do…?yes,…used.? no,…use(d)n’t. yes,…did.? no,…didn’t.ii.情态动词的重点知识表示“能力、许可”的can和may表示能力的情态动词用can/coulda computer_____think for itself; it must be told what to do.a.can’t??????? b.mustn’t???? c.may not??? d.might not表示许可时用may/might ,can/could 都可以，但在问句中用could…?或might…？ 以使口气委婉客气，其回答一定要用can或may，以使回答口气明确（must表示一定，必须，mustn’t表示禁止，不许可）。①—could i call you? by your first name??? —yes, you______a.will????? b.could??? c.may??? d.might②johnny, you_____play with the knife, you_____hurt yourself.a.won’t/can’t????????? b.mustn’t/may c.shouldn’t/must?????? d.can’t/shouldn’t在肯定句中could不可以用来表示过去某一特定场合的能力，而要用was/were able to。the fire spread through the hotel very quickly buteveryone_____get out.a.had to????? b.would?????? c.could?????? d.was able to表示“推断、判断”的canmay,must在肯定句中都可以用来表示可能。在含义上must语气最肯定，may表示的是事实上的可能性。peter______come with us tonight, but he isn’t very sure yet.a.must?????? b.may?????? c.can???????? d.will而can表示的是逻辑上的可能性：mary is in poor health. she can be ill at any times.在否定句中只能用can和may。所以can’t时用以代替mustn’t，语气比may更肯定。中文可以翻译为不可能。michael______be a policeman, for he’s much too short.a.needn’t???? b.can’t?????? c.should????? d.may在疑问句只能用can，不能用may和must。he may be very busy now.?????? can he be very busy now?he must be very busy now.?????? can he be very busy now?
needneed作为情态动词只有一种形式，只用于否定句和疑问句。
daredare作为情态动词用时有两种形式：dare和dared两个词形，除了可以用于否定句和疑问句外，还可以用于条件从句或表示怀疑的句子中。if he dare come,i will kick him out.? i don’t know whether hedare say.注意：he doesn’t dare(to)answer the question.（否定句）does she dare(to)enter the dark room?（疑问句）shall用于第一人称：征求对方的意见。what shall we do this evening?用于第二、三人称：警告、命令、允诺、威胁等。you shall fail if you don’t work harder. 警告he shall have the book when i finish reading.允诺he shall be punished.威胁
should劝告、建议、命令、应该做、道义上的责任。you should(ought to) go to class right away.?? i should(ought to) help him because he is in trouble.
will/would请求、建议，would比will委婉客气。would you pass me the book?表示意志、愿望和决心。i will never do that again.??? they asked us if we would do that againwould可表示过去反复发生的动作或某种倾向。during the vacation he would visit me every weekthe wound would not heal.（伤口老是不能愈合）would表示估计或猜想。it would be about ten when he left home.??? what would she be doing there?情态动词+have done的用法could+have done：本可以做而实际上未能做。you could have done better, but you didn’t try your best.cannot+ have done：表示对现在或过去行为的否定推测。he cannot have been to that town.can+主语+ have done：表示对过去行为的怀疑或不肯定（用在疑问句中）。can he have got the book?might(may)+ have done：对过去发生的行为不太肯定的推测。he may not have finished the work.if we had taken the other road, we might have arrived earlier.must+ have done：对过去发生的行为肯定的推测。其否定式为：cannot have done。you must have seen the film.you cannot have seen the ’t+ have done：本来不必要做的而实际上又做了。you needn’t have watered the flowers,for it is going to rain.注意：didn’t need to(have to)do：没有必要做而实际上也没有做i didn’t need to clean the windows.my sister did it 2 hours ago.should(ought to)+ have done：本来应该做而实际上又没有做。其否定形式表示某中行为不该发生却发生了。you should have started earlier, but you didn’t.she shouldn’t have taken away my measuring tape,for i worked to use it.注意：he should have finished the work by now.（表推测）
虚拟语气
类?? 别
用?? 法
例?? 句
if引导的
条件从句与现在事实相反从句动词：过去式（be用were）主句动词：should/would/could/might+doif he were here, he would help us.与过去事实相反从句动词：had+done主句动词：should/would/could/might+have+doneif i had been free,i would have visited you.与将来事实相反从句动词：过去式/should+动词原形/were+to do主句动词：should/would/could/might+动词原形if it should rain tomorrow, we would not go camping.
省略if的虚拟条件句将虚拟条件从句中的were，had,should放到主语之前，构成主谓倒装①should he come ,tell him to ring me up.②were i you,i would not do it.③had i been free,i would have visited you.
混合虚拟条件句
不同时间的虚拟：各遵守各的规则①if he had listened to me, he would not be in trouble now.②if he had told me yesterday,i should know what to do now.③if i were you, i would have gone to her birthday party.
虚拟与陈述的混合：各遵守各的规则①he could have passed the exam,but he wasn’t careful enough. ②you should have come earlier.the bus left a moment ago.
含蓄虚拟
条件句
but for+名词表示虚拟条件句子或主句中的谓语动词的形式视具体情况而定。这是考查考生应变能力的最佳试题。---but for your timely warning,we ______ into great trouble.---you know we’re friends.a. would get????????? b. must have got??? c. would have got????? d. can’t have got
without+名词表示虚拟条件without the air to hold some of the sun"s heat, the earth at night would be freezing cold.
动词不定式表示虚拟条件it would be only partly right to follow in this way.
如果用这种方式，仅仅对了一半。
现在分词表示虚拟条件having known in time ,we might have prevented the accident.要是及时得知的话，我们也许能阻止这场事故。
过去分词表示虚拟条件given more attention, the tree could have grown better.
如果多留心的话，这树本来可以长的更好。
副词otherwise表示虚拟条件i was too busy at that ,i would have called you.我当时太忙，否则我就给你打电话了。
连词but连接的句子表示虚拟条件he _____fatter but he eats too little .a. would become????? b. would have become? c. must become?????? d. must have become
其它
状语从句as if/as though引导的状语从句中动词用did或had＋done或would/could/might＋do。注意：as if/as though引导的状语从句中也可以用陈述语气：当说话者认为所述的是真实的或极有可能发生或存在的事实时：it sounds as if it is raining.听起来像是在下雨。
he talks as if he is drunk.从他谈话的样子来看他是醉了。①与现在事实相反he talks as if he knew where she was.②与过去事实相反he talks about rome as if he had been there before.③与将来事实相反he opened his mouth as if he would say something.in order that/so that引导的状语从句中动词用can/could/may/ might/ would等+doturn on the light so that we can see it clearly.
宾语从句demand, suggest, order, insist后接的从句中动词为should+dohe suggested that we not change our mind.wish后的从句中分别用过去式，过去完成式和should/would+do表示与现在，过去和将来情况相反i wish i could be a pop singer.i wish i would have gone to shanghai last month.
主语从句在it is necessary / important / strange that…it is suggested / demanded/ ordered / requested that…等从句中，谓语动词用should+doit is strange that such a person should be our friends.
其它
句型中it is time that…句型中动词用过去式或should+doit’s high time that we left/should leave.would rather所接的从句中动词用过去式或者过去完成式i would rather you stayed at home now.if only句型中动词常用过去式或者过去完成式，表示强烈的愿望if only our dream had come true!
h.dare
dare既可用作情态动词，也可用作行为动词，指勇气和胆量上的可能，可译为“敢”。
1.情态动词dare
①dare作为情态动词时主要用于疑问句和否定句，一般不用于肯定句中。
i dare not daren"t walk through the forest at night.
我不敢在黑夜穿过森林。
--- dare you walk through the forest at night
你敢在黑夜穿过森林吗？
--- yes, i dare.
是的，我敢。
--- no, i daren"t.
不，我不敢。
he dare not drive too fast on the rainy day.
下雨天他不敢开得太快。
he dared not do it last year.
去年他不敢做这事。（dare的过去时为dared）
②可以用于表示怀疑的名词性从句中。
i wonder how he dare say such things.
我真奇怪他怎么竟敢说出这样的话。
we don"t know whether he dare climb the mountain.
我们不知道他是否敢爬那座山。
③可以用于条件状语从句中。
if the enemy dare enter the village, we"ll fight against them to the end.
如果敌人敢进入村里，我们就和他们战斗到底。
if you dare cheat in your exam, i will give you some punishment.
如果你们敢在考试中作弊，我就惩罚你们。
2.行为动词dare
① dare可以作为行为动词，多用于肯定句中，但也可用在疑问句和否定句中
he will dare any danger.
他敢面对任何危险。
he dared me to jump over the stream.
他激我跳过小溪。
did anyone dare to admit it
有人敢于承认吗？
i have never dared (to) go back to take a look.
我再也不敢返回去看一眼了。（否定句中to可省略）
②和其他行为动词一样，dare在句子中要随着主语的人称和数发生变化。
he doesn"t dare to walk at night.
他不敢走夜路。（作行为动词）
he daren"t walk at night.
他不敢走夜路。（作情态动词）
does he dare to walk at night
他敢走夜路吗？（作行为动词）
dare he walk at night
他敢走夜路吗？（作情态动词）
he didn"t dare to walk at night fifteen years ago.
XX年前他不敢走夜路。（作行为动词）
he daren"t walk (=dared not walk) at night fifteen years ago.
XX年前他不敢走夜路。（作情态动词）
will you dare to do the same experiment tomorrow
明天你敢做同样的实验吗？（作行为动词）
dare you do the same experiment tomorrow？
明天你敢做同样的实验吗？ （作情态动词）
必背：
英语口语中dare的几个常用结构：
● i dare say...
我想， 大概， 可能， 或许……
i dare say things will improve.
我想情况会好转的。
● how dare you ...
你怎么敢……？
how dare you ask me such a question
你怎么敢问我这样的问题？
● i dare you ...
我谅你也不敢……
i dare you to tell your parents!
我谅你也不敢告诉你父母！
i.need
1.情态动词need
need 和dare一样，作为情态动词时，主要用于否定句和疑问句，一般不用于肯定句中（在肯定句中常被 must, have to, ought to, should等情态动词取代）。作为情态动词，它的词形只有need一种形式。
you needn"t return the book now. you can keep it till next week if you like. 你现在不必还书，??如果愿意，你可以下周还。（needn"t = don"t have to）
need i hand in my homework now
我现在就要交家庭作业吗？
--- need he finish the article next week
他要下个星期完成这篇文章吗？
--- yes, he must.
是的，他必须完成。
--- no, he needn"t.
不，他不需要。（= he doesn"t have to）
2.行为动词need
need和dare一样，也可以作行为动词，可用于肯定句、否定句和疑问句中。行为动词need有人称和数的变化。
plant needs water.
植物需要水。
my shirt needs a button.
我的衬衫需要一枚钮扣。
my car needs repairing.
我的车该修理了。
he has grown up. we don"t need to worry about him.
他已经长大了，我们不必为他担心。
you don"t need to buy so many things for the picnic.
你不必为这次野餐买这么多东西。
patience is needed for that job.
干那工作，需要耐心。
提示：
need作为情态动态时，不要用于肯定句中。
【误】she need do her homework by herself. (need作为情态动词时，不用于肯定句中)
【正】she needs to do her homework by herself.
她该独立完成家庭作业。
a. may和might
1.表示请求、许可，常译为“可以”。
在口语中可用can, could代替may，但在正式场合用may。表示允许时，也可用might代替，might不表示过去时，而是表示口气比较婉转。
you may take this seat if you like.
如果你喜欢可以坐这个位置。
maycan could might i have a talk with you
我可以和你谈谈吗？
--- maymight i come into the room to see my mother
我可以进房间看我母亲吗？
--- no, you mustn"t. she needs to have a good rest.
不，你不能进。她需要好好休息。
提示：
may i ... 问句常见的肯定回答和否定回答。
肯定回答
yes, please.
certainly.
yes, of course.
sure.
go ahead, please.
否定回答
no, you can"t. （最常见）
no, you mustn"t. （具有强烈禁止的意思）
please don"t. you"d better not.
i don"t think you can.
i"m sorry it"s not allowed.
2.表示推测，可译为“可能，也许”。
your math teacher maymight be in his office.? ?? ?你们的数学老师可能在办公室里。（一般情况下，might表示的可能性很小）
the light isn"t on. it maymight be broken.
那盏灯没有亮，它可能坏了。
there may might be some ink left in the bottle.
瓶子里也许还剩点儿墨水。
注意：
用may表示推测一般不用于疑问句，在疑问句中通常用can来代替。
can he be at home
他可能在家吗？
--- can it be true
这可能是真的吗？
--- it may be, or may not be.
可能是，也可能不是。
3.用在目的状语从句中，构成谓语。
he wants to take a taxi so that he may get there in time.
他想坐出租车，这样他就能及时到达那里。
i arrived at the airport earlier in order that i might meet him.
我早早地就到了机场为了能接到他。
4. 有时可以用于祈使句表示祝愿。
may you succeed.
祝你成功
may you be happy.
祝你快乐。
may that day come soon.
希望这一天早日到来。
b. can和could
1. 表示能力，可译为“能，会”。
i can swim. 我会游泳。
emily can dance well and her mother could dance well when she was young.
艾米丽舞跳得很好，她妈妈年轻时舞跳得也很好。
the cinema can seat 1,000 people.
这电影院能容纳1，000人。
i could not read such an easy book when i was 7 years old.
我七岁时连如此简单的书我也看不懂。
2. 表示允许、许可，常用在口语中。could比can语气上要客气。
--- could i use your dictionary
我可以用一下你的字典吗？
---yes, go ahead.
可以，用吧。（或yes, you can. 但不能说yes, you could.）
could can you tell me how to get to the zoo
劳驾，你能告诉我怎么去动物园吗？
he asked me whether he could take the book out of the reading room.
他问我可不可以把书带出阅览室。
3.表示推测，可用于肯定句（can罕见）、否定句和疑问句，但更常见于疑问句或否定句。在此种用法中can和could没有时态的区别，只是表示可能性的大小，can表示推测的可能性比could大。
can he be ill at home
他会是生病在家吗？
can the story be true
这个故事会是真的吗？
he cannot be at home.
他不可能在家。
you mustn"t smoke while you are walking around in the woods. you could start a fire.
在林子里走时一定不要吸烟，那样可能会引起火灾。
4.表示惊异、怀疑、不相信等态度，主要用于否定句和疑问句中。
how can you be so careless
你怎么这么粗心？
where can could they have gone
他们会去了哪里？
he can"tcouldn"t be over sixty.
他不可能超过60岁。
5.could可以用在虚拟条件句中。
if i could fly, i should be very happy.
如果我能飞， 我会很高兴。
if you had followed my advice, you could have finished it.
如果你当时听我的，你早就做完了。
if you had tried harder, you could have passed your exam.
如果你再努力些，你就能通过考试了。
6.can与be able to的区别
①can表示“能力”时，和be able to相当，许多场合都可以互相替换。但当叙述过去经过一番努力才能完成的事情或前面有特殊说明，表示你有能力时，只能用be able to。
【正】can you speak any foreign languages
你会说外语吗？
【正】are you able to speak any foreign languages
你会说外语吗？
【误】the fire spread the building quickly but everybody could escape.
【正】the fire spread the building quickly but everybody was able to escape.
大火迅速蔓延到整幢大楼，但大家都逃了出来。
【正】the fire spread the building quickly but everybody managed to escape.
大火迅速蔓延到整幢大楼，但大家都想法逃了出来。
②be able to 比can有更多形式。
no one could answer the question.
没人能回答这个问题。（这里could可用was able to 代替）
when he grows up, he will be able to support his family.
他长大后就能养家了。
frank is ill. he hasn"t been able to go to school for one week.
弗兰克病了，已经一周没去上学了。
i"m sorry for not being able to help you in time.
对不起，不能及时帮你的忙。
③could经常和动词see, hear, smell, taste, feel, remember, understand等连用。
when we went into the house, we could smell something burning.
当我们走进屋子时，我们闻到什么东西烧焦了。（不用was able to）
she spoke in a very low voice, but i could understand what she said.
虽然她讲话的声音很低，但我还是明白了她说的话。
④在谈论说话时发生的动作，用can，不用be able to。
【误】look! i"m able to swim.
【正】look! i can swim.
看，我会游泳了！
c.must和have to
1.must表示有做某一动作的必要或义务，强调主观看法，可译为“必须，应该”。
everyone must obey the rule.
人人都必须遵守制度。
we must do everything step by step.
我们必须逐步做每件事。
teachers must be patient enough with their students.
老师必须对学生有足够的耐心。
2.have to 表示因客观需要促使主语不得不做某事。
you can"t turn right here. you have to turn left.
你不能在这里右拐，你必须左拐。
my eyesight is very poor. i have to wear glasses for reading.
我的视力很差，看书时不得不戴眼镜。
you have to pass a test before you can get a driving licence.
你在取得驾照之前必须先通过考试。
提示：
在口语中，我们可以使用have got to来代替have to.
i"ve got to work on sunday.
我不得不星期天工作。
when has ann got to go
安必须什么时候走？
3.must 与have to的比较。
must 与have to在表示“必须”这个意思时意义相近，但在用法上有所区别。
①must含有说话者的强烈决意（表示主观的看法），have to 则表示外力环境或习惯使然（即表示客观的必要，作“不得不”解）。
i must study hard.
我必须努力学习。（发自内心的决定）
i have to study hard.
我不得不努力学习。（外界因素逼迫）
you must stay for supper.
你必须留下来吃晚饭。（because i want you to）
you have to stay for supper.
你得留下来吃晚饭。（because there is nowhere else to go）
②must只有一种形式，而have to可有多种时态。
they had to put off the sports meet due to the bad weather.
由于坏天气，他们不得不推迟运动会。
these last two days he has had to take a rest at home.
这两天他必须一直在家休息。
③must的否定式和have to的否定式的意思完全不同。
you must keep it a secret. you mustn"t tell anyone.
你必须保密，你不可以告诉任何人。（mustn"t表示“禁止”）
you don"t have to tell me the secret. 你不必告诉我这个秘密。
（don"t have to意思是“没有必要”= don"t need to）
4.must用于表示推测，它的肯定程度比may, might, could大得多，一般只用于肯定句。
①must do (这里的do通常是状态动词或系动词) ，表示对现在状态的推测。
he must be very lazy for his desk is very untidy.
他肯定很懒，因为他的课桌很不整洁。
carol must get very bored with her job. she does the same thing every day.
卡罗尔肯定对她的工作厌烦了，她每天都做同样的事。
②must be doing表示对现在动作或状态的推测。
put on more clothes. you must be feeling cold with only a shirt on.
多穿点儿衣服，你只穿一件衬衣，肯定觉得冷。
③must have done表示对过去的动作或状态的推测。
the ground is wet. it must have rained last night.
地面是湿的，昨晚肯定下雨了。
i didn"t hear the phone. i must have been asleep.
我没听见电话铃响，我一定是睡着了。
提示：
must表示推测只用于肯定句，否定句和疑问句要用can, could来代替must。
he"s just had his lunch. he can"t be hungry already.
他刚吃过午饭，不会饿的。
they have just arrived here. they can"t know many people.
他们刚到这里，不可能认识很多人。
leslie walked past me without speaking. he can"tcouldn"t have seen me.
莱斯利从我身边走过而没打招呼，他肯定没看见我。
5.must可用来表示根据逻辑推理必然要发生的事，可译为“必然会，总是会”。
we all must die.
我们都会死。
truth must be out.
真相必然会大白的。
winter must be followed by spring.
冬天到了，春天还会远吗？
6.must有时可用来表示“偏偏”的意思。
why must it rain today
为什么偏偏在今天下雨？
when i was taking a nap, a student must knock at the door.
正当我午睡时，偏偏一个学生在这个时候来敲门。
第九章? 情态动词
我们使用语言有时需要提出要求、意向或建议，有时需要表达我们的愿望和打算。我们也可能想更礼貌一些，更得体一些。为了表达上述意义我们需要一组叫情态动词的动词。情态动词有时又叫情态助动词。情态动词本身虽有一定词义，但不能独立用作谓语、也没有人称和数的变化，其后一定要跟随动词原形，共同构成复合谓语。
一、情态动词的特点及形式
情态动词是用于表示说话人的某种感情或语气的词类，有自己的词义，但是不能单独作谓语 ，而必须与其他原形动词共同构成谓语。
情态动词没有人称和数的变化(因此单数第三人称不加s)，有过去式，但无分词形式。
经常使用的情态动词有：can, may, must, ought to, will, shall, would, should, need , dare等。它们的不同形式分别表示请求、允诺、愿望、命令、能力、需要、拒绝等情感和态度。
例如：
you may come in now.
你现在可以进来。(表示“许可”)
the schoolbag can hold so many books.
这个书包能装下这么多的书。(表示“能够”)
you must be here on time.
你必须准时到这儿。(表示“必须”)
you mustn"t make a friend with such a man.
你绝不能与这样的人交朋友。(表示“禁止”)
二、情态动词的用法
1.can, could, be able to
(1)can表示能力，其疑问形式表示请求，其否定形式常表示猜测。can只有现在时和过去时 两种形式，其他时态只能用be able to进行表达。
can i sit here?
我可以坐在这里吗？(表示“请求”)
she could play the violin well when she was a little girl. (表示“过去的能力”)
她很小的时候就能出色地演奏小提琴了。
they have not been able to beat the brazilian team.
他们没有能够打败巴西队。(完成时用be able to表示)
she can"t be there now.
她现在不可能在那里。(表示“猜测”)
(2)could用于疑问句，表示比can更为客气的语气；could用于肯定句可以表示没有多大把握 的猜测或表示过去曾有过的能力；could还可用于虚拟语 气表示与现在情况相反的假设。
could i sit here?
我可以坐在这里吗？(比can更为客气的请求)
she could be serious, but i don"t think so.
她可能是认真的，但我不这样认为。
we wish we could go to the moon like the two americans.
我们要是能像那两个美国人一样也去月球看看多好啊。(虚拟语气)
she could type 100 words within one minute in her twenties.
她二十多岁的时候，能够在一分钟之内打一百个字。(表示过去的能力)
(3)was (were) able to与could的区别是表示不但有能力，而且曾经做过某件事情。
he was able to swim across the yangtze river last summer.
他去年夏天能够游过长江。
he was able to leave germany for america during the world war 2.
在二战期间，他设法离开德国去了美国。
2.may， might
may用于陈述句表示“可以”，“允许”的意思；还可以表示“可能”。例如：
you may sit down.
你可以坐下。(表示“允许”)
you may be correct.
你可能是正确的。(表示“猜测”)
may用于疑问句表示“请求”；用于否定句表示说话人“不允许”，“不许可”。
may i take the dictionary away?
我可以把这本词典拿走吗？(表示“请求”)
you may not take it away.
=i don"t want you to take it away.
我不允许你把它拿走。(表示“拒绝”)
注意：may引导的疑问句，肯定回答用：yes, you may.否定回答用： no, you mustn"t. (no, you can"t或no, you had better not.)表示“千万不要”，“不可 以”，“禁止”的意思。
may i come in?
我可以进来吗？
yes, please.????? no, you mustn"t.
请进。??????????? 不，不行。
might(could)用于一般现在时，表示更为委婉和礼貌的语气。
i"m afraid it might rain this evening.
我看今晚恐怕要下雨。
might i ask a question?
我可以提个问题吗？
might可用于表示与现在的事实相反情况的虚拟语气。
if the boy were older, he might understand.
要是这孩子年龄再大一些，他就可能懂了。
if i were you, i might finish it earlier.
如果我是你，我会更早一些干完这件事。
may和 might用于从句中表示目的，意为“以便能……”、“使……可以”。he wrote? down my address so that he might remember it well.他把我的地址写下来了，以便能记住。
3.must, have to
must强调个人的意志和主观的决心，意为“一定，必须”； have to侧重于客观上 的必要，强调客观条件作用的结果，意为“务必，不得不”。如果用于过去时或将来时 ，要用have to来代替，但must可用于间接引语，表示过去的必要和义务。
you must stop smoking.
你必须把烟戒掉。(强调主观意志)
you must complete the painting before next friday.
你必须在下星期五以前完成这幅画。(强调主观)
i have to stop the car and wait for the policeman.
我不得不停车等那个警察。(强调客观)
there was little time left and she had to drive quickly to the airport.
剩下的时间不多了，她只得开快点赶往机场。(用于一般过去时)
you"ll have to wait for me for a little while tomorrow.
你明天得稍微等我一会儿。(用于将来时)
she said she must do well in her english.
她说她必须要把英语学好。(用于间接引语)
must构成的疑问句，回答的否定形式经常是needn"t或don"t have to，意为“不必要”，“不用……”，而不说mustn"t(除非特别强调)。
must i hand it in before five?
我必须在五点钟以前把它交上去吗？
yes, you must.??? no, you needn"t.
是的，必须交。? 不，用不着。
must的肯定句，还经常用于表示推测。
he must be at home.
他肯定在家里呢。(对现在情况的推测)
they must have gone back to their hometown.
他们一定是回老家去了。(对过去的事的推测)
they must be repairing your car at the garage.
他们肯定在车间修你的车呢。(对现在的行为的推测)
4.need
need可以作情态动词使用，也可作行为动词使用。
作为情态动词使用，need没有时态与人称的变化，并且多在否定句，疑问句和条件句中使 用，含义为“需要，必须”。
you need not hand in the exercise today.
你不必今天交作业。(=i don"t think you need hand in the exercise today.)
need we find time to go into the question?
要不要我们找时间把这个问题深入研究一下？
(=do you think we need find time to go into the question?)
if you need repair your car, come to me.
如果你需要修车，就来找我。
need 作情态动词时的用法，情态need 表需要，没有时态、数、人称，其后直接跟动词，用于疑问和否定。
注意：①need作为情态动词，一般不在肯定句中使用。在肯定句 中通常用must, have to, ought to, should等。例如：
need i tell mr. li about it?
我是否需要把这件事情告诉李先生？
(否定回答)no, you needn"t.
不，没有必要。
(肯定回答)yes, you must. you must tell him about it.
是的，你必须把这件事情告诉他。
②这里“need i...?”与“must i...?”在意思上差别不大，因此回答也是一样的，肯定为 must，否定用needn"t。
③needn"t+ have done表示“做了本不需要做的事”。例如：
you needn"t have completed so many exercises.
你本来不必完成这么多习题。(实际已经做完了)
she need"t have gone there with him.
她本来没有必要和他一块去那里。(实际已去了)
need作实义动词(或称行为动词)使用时，其句型变化与其他行为动词一样，要加助动词do , does, did等等。例如：
i need your help.
我需要你的帮助。
do you need anything to eat?
你要不要吃点东西？
she doesn"t need to take any medicine.
她不需要吃药。
注意：
need作为动词使用，宾语可以是动名词或不定式；动名词用主动形式，而不定式一定要接用被动形式。例如：
this car needs repairing.
(=this car needs to be repaired.)
这辆汽车需要修理。
does this shirt need washing?
(=does this shirt need to be washed?）
这件衬衣需要洗吗？
5.should， would
should后接原形动词表示应该做某事或承担责任、义务；should还可以表示一种推测。
例如：
you should work harder and pass the exam.
你应该更加努力，通过考试。(表示应该)
he should brush his teeth before going to bed.
他应该睡觉以前把牙刷一下。(表示应该)
she should have arrived in hong kong by this time.
她这时候已经到香港了。(表示推测)
the book is written by a famous professor, so it should be selling well.
(表示推测)
这本书是一位著名教授写的，应该很有卖点。
would有两种用法：
①多用于一般现在时，表示比will更为婉转的请求。
②用于一般过去时，表示过去的习惯性行为。
例如：
would you like a cup of tea?
来一杯茶好吗？(婉转的请求)
would you show me the way to the post office?
请告诉我去邮局怎么走好吗？(请求)
when even they came to see him, they would bring him a lot of farm products.
无论何时他们来看他，总会给他带来许多农产品。(表示过去的习惯)
each time he passed the food shop, he would buy some chocol ate for his daughter.
每次路过食品店，他都会给女儿买些巧克力。(表示过去的习惯)
6.would， used to
would和used to都表示过去的习惯和过去反复发生的动作，但would只强调过去的情况，后 面通常接表示动作的动词不能接表示状态的动词。而used to强调过去的情况与现在的情况 的对比，说明现在情况不同了。
each time his mother"s birthday came, he would buy her a present .
每次到他母亲生日的时候，他都要给她买一件礼物。(表示过去的习惯)
my father used to go to the office by bike when he was young.
我父亲年轻的时候总是骑车去上班。(现在不是这样了)
when he had a meal at this restaurant, he would sit at the table? by the window.
当他在这家餐厅吃饭时，总是坐在靠窗的桌子边。(过去的习惯)
he used to drink so much when he lost his job.
当他失业时，他酗酒很厉害。(现在不酗酒了)
比较：must, may和might用于表示猜测的区别：
must表示最大的可能性，意思是“必定，一定，肯定”；
do you notice the way the man speaks? he must be a business man.
你注意到这个人说话的方式了吗？他一定是一个商人。
look at the fire over there! something must be happening to mr. cameron"s house.
看那边的大火！肯定是卡梅隆家出事了。
someone must have told you the news yesterday.
昨天一定是有人已经告诉了你这个消息。
may表示的可能性小于must，意为“可能”。
the opportunity may come at any time.
机会可能会随时到来的。
go to miss li and she may help you with it.
去找李老师，她可能会帮助你解决此事。
your parents may know nothing about it.
你父母对此可能一无所知。
might表示的可能性最小，意为“也许，大概”。might表示可能性，不含有过去时的意思。
they might be at susan"s house.
他们也许都在苏姗家呢。
your mother might be angry with you.
你妈妈大概生你的气了。
mr. cameron might refuse to attend the meeting today.
卡梅隆先生今天可能会拒绝出席会议。
7.dare
dare作为情态动词，意为“敢于，敢做……”，多用在否定句、疑问句或条件状语从句中。
例如：
the girl dare not stay here alone in this empty house.
这个姑娘不敢独自一人呆在这所空房子里。
dare you swim across the river?
你敢游到河那边去吗？
how dare you do such a thing?
你怎么敢做这样的事情？
i don"t know if she dare say that to him.
我不知道她敢不敢跟他说那话。
三、情态动词+have+ done的用法
1. must have done与can"t (couldn"t) have done
must have done用于表示对过去的肯定推测，只能用于肯定句，表示“一定……，肯定已经 ……”；而can"t (couldn"t) have done用于表示对过去的否定的推测，用于否定句， 表示“不可能……”。
look at your school report. you must have made a lot of mistakes in your test papers.
看看你的成绩单。你一定是在试卷上出了好多错。
she suddenly fell down on her way to school, she must have been ill.
她在去上学的路上突然摔倒了，肯定是生病了。
he can"t have been in his office this time yesterday.
昨天这个时间他不可能在他的办公室里。
she couldn"t have seen me because i wasn"t there at all yesterday.
昨天她不可能看见我，因为我根本没在那里。
2.may (might) have done
该结构只用于肯定句或否定句之中，表示对过去情况的猜测，意为“也许”，“已经”，“ 本来可以”等。其否定形式含义为“大概不会”，“可能不是”等。而疑问句形式要用can 或could来 提问。
he may have arrived in america by now.
到这时候他可能已经到达美国了。
i might have told you about the things earlier.
我本来可以早一些告诉你这些情况的。
i might have lent him more money when he came to me.
当他来找我时，我本可以多借给他一些钱。
could he have returned it?
他不会不还这些钱吧？
3.ought to have done与should have done
这两种结构都表示过去必须做的事而没做，含有“本来应该怎样”的意思。
you ought to have gone into this question earlier.
你本来应该再早一些深入研究一下这个问题。
they ought to have prepared the work for the meeting more carefully.
他们本该把会议工作准备得更充分一些。
he should have done better in the car race.
他本应该在汽车大赛之中表现得更好一些。
we should have climbed up to the top of the mountain.
我们本来应该爬到山顶的。
4.needn"t have done
该结构表示过去不需要做的事情，但却已经做了，含有“本来不必怎样”的意思。
you needn"t have done it instead of him yesterday.
你昨天原本不必替他做那件事情的。
he needn"t have given her so much money at that time.
那时他本来不必给她那么多的钱。
there were plenty of time, she needn"t have hurried.
时间很充裕，她本不必匆忙
1 情态动词的语法特征
1） 情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
2） 情态动词 除ought 和have 外，后面只能接不带to 的不定式。
3） 情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4） 情态动词没有非谓语形式，即没有不定式，分词，等形式。
2 比较can 和be able to
1）can could 表示能力；可能 (过去时用could),
只用于现在式和过去式(could)。be able to可以用于各种时态。
they will be able to tell you the news soon. 他很快就能告诉你消息了。
2）只用be able to
a. 位于助动词后。
b. 情态动词后。
c. 表示过去某时刻动作时。
d. 用于句首表示条件。
e. 表示成功地做了某事时，只能用was/were able to， 不能用could。
he was able to flee europe before the war broke out.
= he managed to flee europe before the war broke out.
注意：could不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。
--- could i have the television on?
--- yes, you can. / no, you can"t.
2）在否定，疑问句中表示推测或怀疑。
he couldn"t be a bad man.
他不大可能是坏人。
3 比较may和might
1） 表示允许或请求；表示没有把握的推测；may 放在句首，表示祝愿。
may god bless you!
he might be at home.
注意： might 表示推测时，不表示时态。只是可能性比may 小。
2）成语： may/might as well，后面接不带to 的不定式，意为"不妨"。
if that is the case, we may as well try.
典型例题
peter ___come with us tonight, but he isn"t very sure yet.
a. must b. may c. can d. will
答案b. 表可能性只能用may. 此句意可从后半句推出。
4 比较have to和must
1) 两词都是"必须"的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。
my brother was very ill, so i had to call the doctor in the middle of the night. 我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事)
he said that they must work hard. 他说他们必须努力工作。（主观上要做这件事）
2) have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
he had to look after his sister yesterday.
3） 在否定结构中： don"t have to 表示"不必"
mustn"t 表示"禁止"，
you don"t have to tell him about it. 你不一定要把此事告诉他。
you mustn"t tell him about it. 你一定不要把这件事告诉他。
5 must表示推测
1) must用在肯定句中表示较有把握的推测，意为"一定"。
2) must表对现在的状态或现在正发生的事情的推测时， must 后面通常接系动词be 的原形或行为动词的进行式。
you have worked hard all day.you must be tired. 你辛苦干一整天，一定累了。（对现在情况的推测判断）
he must be working in his office. 他一定在办公室工作呢。
比较：
he must be staying there.
他现在肯定呆在那里。
he must stay there.
他必须呆在那。
3) must 表示对已发生的事情的推测时，must 要接完成式。
i didn"t hear the phone. i must have been asleep. 我刚才没有听到电话，我想必是睡着了。
4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。
---why didn"t you answer my phone call?
---well, i must have been sleeping, so i didn"t hear it.
5) 否定推测用 can"t。
if tom didn"t leave here until five o"clock, he can"t be home yet. 如果汤姆五点才离开这儿，他此时一定还未到家。
6 表示推测的用法
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。
表示对现在或将来正在进行的情况进行推测。
at this moment, our teacher must be correcting our exam papers.
这时，我们老师想必在批改试卷。
3）情态动词+动词完成时。
表示对过去情况的推测。
we would have finished this work by the end of next december.
明年十二月底前我们很可能已完成这项工作了。
the road is wet. it must have rained last night.
地是湿的，昨天晚上一定下雨了。
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。
your mother must have been looking for you.
你妈妈一定一直在找你。
5）推测的否定形式，疑问形式用can"t, couldn"t表示。
mike can"t have found his car, for he came to work by bus this morning.
迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。
注意：could, might表示推测时不表示时态，其推测的程度不如 can, may。
7 情态动词+ have +过去分词
1) may(might) have + done sth, can (could) have + done sth 表示过去，推测过去时间里可能发生的事情。
philip may (might) have been hurt seriously in the car accident.
philip can (could) have been hurt seriously in the car accident.
2) must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有"肯定"，"谅必"的意思。
--- linda has gone to work, but her bicycle is still here.
---she must have gone by bus.
3) ought to have done sth, should have done sth
本应该做某事，而事实上并没有做。否定句表示"不该做某事而做了"。
you ought to (should) have been more careful in this experiment.
he ought not to have thrown the old clothes away.（事实上已扔了。）
ought to 在语气上比should 要强。
4) needn"t have done sth 本没必要做某事
i dressed very warmly for the trip, but i needn"t have done so. the weather was hot.
5) would like to have done sth 本打算做某事
i would like to have read the article, but i was very busy then.
8 should 和ought to
should 和ought to 都为"应该"的意思，可用于各种人称。
---ought he to go?
---yes. i think he ought to.
表示要求，命令时，语气由 should（应该）、had better最好）、must（必须）渐强。
9 had better表示"最好"
had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
had better do sth
had better not do sth
it is pretty cold. you"d better put on my coat.
she"d better not play with the dog.
had better have done sth表示与事实相反的结果，意为"本来最好"。
you had better have come earlier.
10 would rather表示"宁愿"
would rather do
would rather not do
would rather… than… 宁愿……而不愿。
还有would sooner, had rather, had sooner都表示"宁愿"、"宁可"的意思。
if i have a choice, i had sooner not continue my studies at this school.
i would rather stay here than go home. = i would stay here rather than go home.
典型例题
---- shall we go skating or stay at home?
----which ___ do?
a. do you rather b. would you rather c. will you rather d. should you rather
答案b。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句， would 提前，所以选b。
11 will和would
注意：
1）would like； would like to do = want to 想要，为固定搭配。
would you like to go with me?
2）will you…? would you like…? 表示肯定含义的请求劝说时，疑问句中一般用some, 而不是any。
would you like some cake?
3）否定结构中用will，一般不用would, won"t you是一种委婉语气。
won"t you sit down?
12 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…? /don"t have to.
典型例题
1）---could i borrow your dictionary?
---yes, of course, you____.
a. might b. will c. can d. should
答案c.could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用could或might。复习： will 与you连用，用来提出要求或下命令。should与you 连用，用来提出劝告。
2）---shall i tell john about it?
---no, you ___. i"ve told him already.
a. needn"t b. wouldn"t c. mustn"t d. shouldn"t
答案a。needn"t 不必，不用。 wouldn"t 将不， 不会的。 mustn"t 禁止、不能。 shouldn"t 不应该。本题为不需要，不必的意思，应用needn"t。
3）---don"t forget to come to my birthday party tomorrow.
---______.
a. i don"t b. i won"t c. i can"t d. i haven"t
答案b. will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，选b。
13 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 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.?
ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do
等助动词协助。
典型例题
tom ought not to ___ me your secret, but he meant no harm.
a.have told b.tell c.be telling d. having told
答案a。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词 ought to 后，所以用 have。
14 比较need和dare
这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面的不定式必须带to，而dare作实义动词用时， 后面的to 时常可以被省略。
1) 实义动词： need （需要， 要求）
need + n. / to do sth
2) 情态动词： need，只用原形need后加do，否定形式为need not。
need you go yet?
yes, i must. / no, i needn"t.
3) need 的被动含义：need, want, require, worth（形容词）后面接doing也可以表示被动：
need doing = need to be done
导学案4情态动词（ii）
一、ought to? 应该，应当????? 其否定 “ought not to” 或 “oughtn’t to”
(1) 用于第一人称，表有责任或有必要做某事。
we ought to be more careful with our homework.
(2) 用于二、三人称，表建议或劝告。
you ought to follow your teacher’s advice.
she ought not to go alone.
(3) ought to+have done: 本该……
i’m sorry. i ought to have told you this morning.对不起，我本该今天早上告诉你的。
二、have to / don’t have to / mustn’t
(1) have to = have got to? 必须，不得不?? （有人称和数、时态的变化）
he has to work on the farm all day .? 他不得不在农场工作一整天。
（2）don’t have to? 不必……
you don’t have to buy a computer.
(3) mustn’t?? 禁止，不许
you mustn’t sleep in class!
三、need 需要，必要（既可以作情态动词，也可以作实义动词，但用法不同）
（1）作为情态动词，need 通常用于否定句和疑问句
①you needn’t buy the book..
②——need he do his homework first?
——yes ,he must!???????? (no ,he needn’t)
(2) need 作为实义动词时，通常用法是：
sb/sth need to do (表主动)?????????????? we need to tell him the truth.
sb/sth need doing /to be done（表被动） my car needs repairing./my car needs to be repaird
sb need sth?? 某人需要……?? mary needs your help.
三、情态动词+have done
1. must have done??? 推测过去“肯定……”
he must have played computer games last night.
2 may / might have done 推测过去“也许……”
he might have known the answer to the question.
3.(1)could have done 用于疑问句时，表示? 推测过去“可能……？”
could he have finished the task? 他可能把任务完成了吗？
（2）could have done 用于肯定句时， 表“能够做而没有做”
i could have finished the work on my own. 我本能够独自完成工作。
4. (1)should have done 本应该做而没有做
you should have studied hard.
(2) shouldn’t have done 本不该做而做了
you shouldn’t have told lies.
5. ought to have done: 本该做而没做
6. needn’t have done? 本不必……??? 本没必要……
you needn’t have told me the news.
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