一、情态动词
情态动词具有一定的词义, 没有人称和数的变化, 必须和其他动词一起构成谓语, 用来表示愿望、态度或推测等。
You may use my dictionary. 你可以使用我的字典。(表示“允许”)
You can't have seen him just now. He has been abroad for nearly a month. 你刚才不可能看见他了, 他已经出国近一个月了。(表示“推测”)
(一)表能力
表现在的能力
can
am/is/are able to
表将来的能力:will be able to
表过去的能力
could 表示过去的能力, 不表示是否做
was/were able to 表示过去有能力做并且成功地做了, 相当于:managed to do sth./succeeded in doing sth.
could have done 表示过去本来能够做但未做
I can't promise anything, but I'll do what I can. (现在的能力)我不能许诺什么, 但我会尽力而为。
If you have a good sleep, you will be able to work out this problem. (将来的能力)
如果你好好睡一觉, 你将能够解出这道题。
The fire spread through the hotel very quickly but everyone was able to get out. (过去有能力做并且成功地做了某事)
尽管这场大火迅速蔓延到了整个宾馆, 但是每个人都逃了出去。
I could have worked out the problem, but I was too nervous. (本来有能力做但未做)
我本来可以解出这道题, 但我太紧张了。
(二)表推测(可能性)
1. 可能性可分为客观的可能性和具体事情实际发生的可能性两种。客观的可能性并不表示具体某事是否会发生, 而用来说明人或事物的特征∙∙∙∙∙∙∙∙∙。
情态动词can 可用于肯定句中表示客观的(或理论的) 可能性, 而表示具体事情实际发生的可能性时, can 一般不用于肯定句。
Accidents can happen on such rainy days.
在这样的多雨天气里可能会发生事故。(客观的可能性)
We may go to the cinema tonight, but we are not sure yet.
今晚我们可能去看电影, 但还没确定。(实际可能性, 不用can)
2. 表示具体事情实际发生的可能性
表示具体事情实际发生的可能性的层次(由强及弱)比较(见下表)
1)在肯定句中表推测(must/have to, should/ought to, may, might, could)
①当说话者表达怀疑或犹豫之意时, 需用may、might 或could, 其中might、could 比may 所表达的怀疑或犹豫之意更强。
That may be our taxi now!
现在那辆可能就是我们的出租车了!
That could/might be our taxi(but I doubt it).
那辆有可能是我们的出租车(但我有所怀疑)。
②当说话者表达毫无疑问的结论时, 需用must 和have to(较通俗), 意为:一定, 肯定; should 和ought to 所表达的程度不如must 强, 但比may, might 和could 强, should/ought to 表示推测出合乎理想的情况或结果, 意为:按说应该。
He must/has to be the wanted man:He's exactly like the one in this picture. 他一定是被通缉的那个男子:他和这张照片上的人一模一样。
He ought to/should be here on time—he started early enough.
他应该按时到这里的———他出发得够早的。
2)在否定句中表推测(may not, might not, shouldn't, can't, couldn't)否定语气较弱时, 常用should not(应该不会), 或用may not, might not(可能不, 也许不); 否定语气较强时, 则用can't 或couldn't(不可能)。
Don't worry. Your father may not have been hurt seriously.
别担心, 你父亲也许∙∙伤得不∙厉害。
There shouldn't be any difficulty in getting you a visa.
给你弄个签证应该不会∙∙∙∙有什么困难。
3)在疑问句中表推测(can, could)
can, could 在疑问句中, 常表示困惑、不相信等。
There's someone outside—who can it be?
外面有人———会是谁呢?
What can they be doing?
他们可能在干些什么呢?
Could he be serious?
他是当真的吗?
Where can she have put it? 她能把它放在哪儿呢?
题组训练 用情态动词或所给词的适当形式填空
①(2014 大纲全国, 30) Although you can find bargains in London, it's not generally a cheap place to shop.
②(2014 江西, 30) Life is unpredictable; even the poorest may/might become the richest.
③ (2013 辽宁, 31) Harry is feeling uncomfortable. He must have drunk (drink) too much at the party last night.
(三)表示必要性、义务、责任
1. 必要性
现在或将来必须做某事:must/have to + do sth.
现在或将来不必做某事
don't have to do sth.
needn't do sth.
过去没必要做某事但做了:needn't have done sth.
You needn't have worked that late last night. It was harmful to your health.
你昨晚本来不必工作到那么晚的。那对你的健康有害。
—Must I give up smoking?
—Yes, you must./No, you needn't.
———我必须戒烟吗?
———是的, 你必须。/不, 你不必。
2. 义务、责任
should 意为“(义务上)应该”, 在语气上比must(必须)弱。
“should + 动词原形”表示现在或将来应该……; “should + have + 过去分词”表示过去本该……。
I should go and visit him this afternoon, but I wonder if I will be free.
今天下午我应该去看望他, 但我不知道我是否有空。(表示将来应该)
You should have come to the conference yesterday. What was the reason for your absence?
你昨天本应该参加那个会议。你缺席的原因是什么? (表示过去本该)
题组训练 用情态动词填空
④(2014 湖南, 25)—I've prepared all kinds of food for the picnic.
—Do you mean we needn't bring anything with us?
⑤—Sorry, Professor Smith. I didn't finish the assignment yesterday.
—Oh, you should have done it as yesterday was the deadline.
(四)表示请求、建议、命令、允许、禁止
1. 表示请求、建议
1) 表示请求许可(asking for permission) 或提出建议时(making suggestions)用:
May/Can/Could/Shall I/we... ?
Can(Could)/Will(Would)you... ?
Shall he/she/they... ?
—May I sit down?
—No, you mustn't.
———我可以坐下吗?
———不可以。
Shall the driver wait outside?
司机在外边等着可以吗?
Would you do me a favor?
请帮我一下, 好吗?
注意:
请求对方许可时, could 表委婉的语气, 回答时要用can。
—Could I use your bike tomorrow morning?
—Yes, you can. (否定:No, I'm afraid not.)
———明天早晨我用一下你的自行车, 行吗?
———行, 你用吧。(否定:不, 恐怕不行。)
2)主动提出帮忙(making an offer)时用:Shall I/we... ?
—What's your name?
—Khulaifi. Shall I spell it for you?
———你叫什么?
———Khulaifi。我为你拼出来好吗?
2. 表示命令、允许、禁止
must(必须), mustn't(禁止)可以表示说话者的命令或指令, 语气比较强烈; should/ought to(应该), shouldn't/oughtn't to(不应该)也可表示说话者的命令、指令, 但暗含对对方是否听从并无把握; may/might, can 表示允许。
The children must be back by 4 o'clock.
孩子们必须在4 点钟以前回来。
You mustn't leave the gate open. 你不要让大门敞开着。
You ought to/should apologize.
你应该道歉(虽然我不知道你是否会这样做)。
You oughtn't to/shouldn't neglect the garden.
你不应该疏于照管花园。
You may/can/might come if you wish.
你想来就来吧。
Passengers may/can/might cross by the footbridge.
乘客可通过步行桥穿过去。
题组训练 用情态动词填空
⑥(2014 北京, 27) Can/May I have a word with you? It won't take long.
⑦—The room is so dirty. Shall we clean it?—Of course.
(五)表示意愿、意志、决心、允诺
1. shall 与第二、三人称连用, 用于陈述句中, 表示说话者的意志, 用来表达说话者给对方以命令、指示或允诺。此外, 当宣布法律、规定时, 也用shall 来表达。
It has been announced that candidates shall remain in their seats until all the papers have been collected.
已宣布, 在所有试卷收上来之前, 应试者必须留在自己的座位上。(规则或规定)
2. will, would 与各种人称连用, 用于陈述句, 表示主语的意愿、意志或决心。
You can stay here as long as you can, if you will. 如果你愿意∙∙,
你能在这里待多长时间就待多长时间。(表示主语的意愿)
—Mr. Gordon asked me to remind you of the meeting this afternoon. Don't you forget it!
—OK, I won't. (表示决心)
———戈登先生让我提醒你今天下午有会议。你可别忘了!
———好的, 我不会忘的。
3. 表示“宁愿做某事”时, 可使用下面这些句式:
would rather do sth.
would rather do sth. than do sth.
would do sth. rather than do sth.
would rather sb. did sth.
prefer to do sth.
prefer to do sth. rather than do sth.
prefer doing sth. to doing sth.
高考中对这类用法的考查主要侧重结构, 因此要熟记这些结构。
题组训练 用情态动词填空
⑧—Why didn't you come to Simon's party last night?
—I wanted to, but my mom simply would not let me out so late at night.
⑨The school rules state that no child shall be allowed out of the school during the day unless accompanied by an adult.
(六)表示习惯和倾向
will(won't)可用来叙述真理, 还可叙述目前的习惯, would(wouldn't)可以用来叙述过去的习惯。
Engines won't run without lubricant.
没有润滑剂发动机就不能运转。
She will listen to records alone in her room for hours.
她独自一人在屋里听唱片, 常常一听就是几个小时。
He would spend hours in the bathroom or on the telephone.
他以前一进洗澡间或是一打电话, 往往就是几个小时。
注意:would 和used to 都可表示过去的习惯, 但前者表示过去反复的动作, 常与every day, often, frequently 等连用; 后者表示
过去的状态或过去的习惯, 但现在已不存在。
When he was abroad, he would read as many books as possible.
在国外时, 他总是尽可能多读书。
She doesn't get up so early as she used to.
她不像以前那样起得那么早了。
(七)need 和dare 的用法
need 和dare 两者既可用作情态动词也可用作实义动词。作实义动词时, 有人称和数的变化, 可用于肯定句、否定句或疑问句中, 构成否定句或疑问句时要用助动词do, does, did; 作情态动词时, 没有人称和数的变化, 直接接动词原形, 多用于否定句和疑问句中, 构成否定句和疑问句时不用助动词。另外, dare 作情态动词时, 还可用于条件状语从句中, 过去式为dared; 作实义动词时, dare 用于疑问句或否定句, 后面的to也可省略; I dare say 是习惯说法, 意为“我想, 大概”。
He needn't do it. (情态动词)
He doesn't need to do it. (实义动词)
他不必做这件事。
I didn't know whether he dared say that to him. (情态动词, 有时态变化)
我不知道他是否敢对他说那些。
He didn't dare(to)do it. (实义动词)
He dared not do it. (情态动词)
他不敢那么做。
注意:need 作实义动词时, 还可表示“需要”, 后接动名词的主动形式或不定式的被动形式表示被动含义。
The floor needs sweeping/to be swept. 地面需要打扫了。
(八)“情态动词 + have done”用法一览表
(九)情态动词的其他用法要点
1. cannot but do sth. 表示“不得不/只好做某事”。
I could not but admit that he was right and I was wrong.
我不得不承认他对了, 我错了。
注意:
表示“不得不/只好做某事”的其他句型:
can't choose but do
can do nothing but do
have no choice but to do
2. can't help(doing) sth. = can't help but do sth. 忍不住做某事。
I can't help thinking about the past.
我不禁回想起过去。
She couldn't help but wonder what he was thinking.
她不禁琢磨着他在想些什么。
3. may well 和may as well 结构。
(1)“may well + 动词原形”是一种常用结构, 意为“完全可能, 很可能”, 相当于“be very likely to + 动词原形”。
He may well win. 他完全可能赢。
Her appearance has changed so much that you may well not recognize her.
她的模样变化太大, 你很可能认不出她了。
(2)“may as well + 动词原形”意为“最好, 倒不如”。
You may as well do it at once.
你最好马上就做这件事。
We may as well stay where we are.
我们待在现在的地方倒也不错。
4. cannot(can + never 等否定词) 与enough, too 连用表示“再……也不为过”。
You cannot be careful enough.
你再细心也不为过。
5. may 可以用于祈使句, 表示祝愿。
May we never forget each other. 愿我们彼此永不相忘。
May you return in safety. 愿你平安归来。
6. should 有时表示说话人对某事不能理解, 感到意外、惊异等, 意为“竟会”。
It's odd that she should think I would want to see her again.
她竟然认为我会想再次见到她, 真奇怪。
7. must 表示“偏要、硬要”。
Must you make so much noise?
你非得这么吵吗?
8. may 作“可以”讲时, 其否定式常用mustn't, 表示“禁止”; must 作“必须”讲时, 其否定式是“needn't”, 表示“不必”。
—May I use your car?
—No, you mustn't.
———我能用用你的车吗?
———不, 不能。
(委婉地拒绝可用:Sorry, but I am using it now. 或You'd betternot. 等)
—Must I work out the problem tonight?
—No, you needn't.
———我今晚必须做出这道题吗?
———不, 不必。
9. won't, can't, doesn't 的区别
The window won't open. 这扇窗户怎么都打不开。(强调实施者执意要打开)
The window can't open. 这扇窗户打不开。(这扇窗户原来设计时就不能打开, 是固定死的)
The window doesn't open. 这扇窗户坏了。(强调这扇窗户质量有问题)
二、虚拟语气
虚拟语气是指说话人表示一种主观愿望或假设的情况。主要用于条件状语从句、主语从句、宾语从句、表语从句、同位语从句和其他的一些句子结构中。
If I had more time, I would help you with your English. 如果我有更多的时间, 我就会帮你学英语了。(表示与现在事实相反的假设)
I wish I were as young as you. 我要是像你一样年轻就好了。(表示一种愿望)
It is strange that he should not have been invited to the meeting. 很奇怪, 竟然没有人邀请他去参会。(用于主语从句)
He insisted that we(should)adopt this teaching method.
他坚持认为我们应该采用这个教学方法。(用于宾语从句)
His idea is that we(should)speak more English in class.
他的建议是我们应该在课上多说英语。(用于表语从句)
The young man followed his doctor's advice that he (should) give up drinking. 那个年轻人接受了医生让他戒酒的建议。(用于同位语从句)
(一)虚拟语气在非真实条件句中的运用
使用虚拟条件句时要注意以下几点:
1. 错综时间条件句
当条件状语从句表示的动作或行为和主句表示的动作或行为所发生的时间不一致时, 被称为“错综时间条件句”, 动词的形式要根据它所表示的时间作出相应的调整。
If you had just followed my advice, you would be better now.
如果你刚才听了我的建议, 你现在就好多了。
If you had studied hard before, you would be a college student now.
如果你以前努力学习的话, 你现在就是大学生了。
2. if 省略句
在虚拟条件状语从句中可省略if, 把were, had, should 提到句首, 变为倒装句式。
If I were at school again, I would study harder.
→Were I at school again, I would study harder.
如果我还有上学的机会, 我会更加努力地学习。
If you had come earlier, you would have caught the bus.
→Had you come earlier, you would have caught the bus.
如果你来得早些, 你就能赶上那辆公共汽车了。
If it should rain tomorrow, we would not go climbing.
→Should it rain tomorrow, we would not go climbing.
如果明天下雨的话, 我们就不去登山了。
注意:若省略的条件状语从句中的谓语动词是否定形式时, 不能用动词的缩略形式。如:我们可以说Were it not for the expense, I would go abroad now. 但不能说Weren't it for the expense, I would go abroad now.
3. 含蓄条件句
有时为了表达的需要, 在虚拟语气中并不总是出现if 引导的条件句, 而是通过其他手段来代替条件句。
Without your help, we couldn't have finished the work ahead of time.
=But for your help, ... =If it had not been for your help, ...
=Had it not been for your help, ...
没有你的帮助, 我们不可能提前完成这项工作。
I was ill that day. Otherwise, I would have taken part in the sports meeting. (副词)
我那天病了。否则, 我就参加运动会了。
He telephoned to inform me of your birthday, or I would have known nothing about it. (连词)
他打电话通知了我你的生日, 否则, 我对此一点都不知道。
I would write to her, but I don't know her address. (连词)
我要给她写信来着, 可是不知道她的地址。
A few hours earlier(=If you had come a few hours earlier), you would have been able to meet the famous writer.
要是你早来几个小时, 你就能见到那位著名的作家了。
4. even if, even though 也可用于虚拟语气, 其形式与if 从句在虚拟语气中的形式相同。
题组训练 用所给词的适当形式填空
⑩(2014 北京, 34) We should/could/would be (be)back in the hotel now if you didn't lose the map.
[11]If he had caught (catch)the morning train, he would not have been late for the meeting.
[12]If we had booked (book) a table earlier, we wouldn't be standing here in the queue.
(二)虚拟语气在名词性从句中的运用
1. 用于宾语从句中
(1)wish 后面的宾语从句一般用虚拟语气, 表示一种不可能实现的愿望。其谓语动词构成形式为:
一般过去时(宾语从句动作与wish 同时)
had + 过去分词(宾语从句动作先于wish)
would/could + 动词原形(宾语从句动作后于wish)
I wish(that)I were a bird and could fly freely in the sky.
我希望我是只小鸟, 能在天空中自由飞翔。
I wish(that)I had met that film star yesterday.
我希望昨天见到那个影星了。
此外, If only + 句子=How I wish + that 从句(that 可省略)。
If only I were a flying bird! = How I wish I were a flying bird! 我要是一只飞鸟该多好啊!
If only I had seen the film! = How I wish I had seen the film! 我要是看了那部电影该多好啊!
(2)用于表示建议、命令、要求等动词后的宾语从句中, 常见的动词有insist, order, command, require, request, demand, advise,
suggest, propose, recommend 等。宾语从句中的虚拟语气结构为“should + 动词原形”, should 可以省略。
He suggested that we(should)start off early the next day.
他建议我们第二天早点出发。
They insisted that the boy(should)go with them.
他们坚决要求那个男孩子跟他们一起去。
此类动词记忆小窍门:
一坚持(insist)
二命令(order, command)
三要求(require, request, demand)
四建议(advise, suggest, propose, recommend)
注意:当suggest 表示“暗示, 表明” 之意, insist 表示“坚持说”之意时, suggest/insist 后的宾语从句不使用虚拟语气, 应使用陈述语气。
The smile on his face suggested that he was satisfied with our work. 他脸上的微笑表明他对我们的工作很满意。
The man insisted that he had never stolen money.
那个人坚持说他从没有偷过钱。
(3)在would rather 后的宾语从句中, 谓语动词用一般过去时(be 用were), 表示对现在或将来的虚拟; 宾语从句谓语动词用过去完成时表示对过去的虚拟。
I would rather they didn't hear of the news.
我宁愿他们没听到那个消息。(对现在或将来的虚拟)
I would rather I had not told him the bad news.
我宁愿没告诉他那个坏消息。(对过去的虚拟)
2. 用于主语从句中
It is desired/suggested/proposed/recommended/necessary/important/strange/natural/a pity/essential + that 从句, 从句的谓语动词用“should + 动词原形”, should 可以省略。
It is suggested that the meeting(should) be put off till next week. 人们建议将会议推迟到下周。
It is strange that he (should) have treated his parents like that. (从句谓语动词的动作在主句谓语动词的动作之前发生时, 要用“should have + 过去分词”, should 可以省略)
真奇怪, 他竟然那样对他父母。
注意:以上句式也可以用陈述语气。
It's a pity that you can't dance.
真遗憾你不会跳舞。
3. 用于表语从句和同位语从句中
在suggestion, proposal, order, plan, idea, request, advice 等名词后的表语从句和同位语从句中要用虚拟语气, 其构成是“should + 动词原形”, should 可以省略。
My idea is that we(should)think it over before accepting it.
我的意见是在接受它之前我们要仔细考虑。
We all agreed to his suggestion that we (should)go to Dalian for sightseeing. 我们都同意他让我们去大连观光的建议。
题组训练 用所给词的适当形式填空
[13]—Where are the children? The dinner's going to be completely ruined.
—I wish they were (be)not always late.
[14] (2014 陕西, 23) We would rather our daughter stayed (stay)at home with us, but it is her choice, and she is not a child any longer.
(三)虚拟语气在as if/as though 引导的从句中的运用
as if/as though 引导方式状语从句或表语从句, 有时从句的谓语部分要用虚拟语气形式, 其形式为:
一般过去时(状语从句动作与主句谓语动词所表达的动作同时发生)
过去完成时(状语从句动作先于主句谓语动词所表达的动作)
would/could/might + 动词原形(状语从句动作后于主句谓语动词所表达的动作)
He looks as if he were an artist. (同时)
他看起来像个艺术家。
She speaks English so fluently as if she had studied English in America. (先于)
她讲英语如此流利, 好像她在美国学过英语。
He learns English so hard as if he would go to the U. S. A. (后于)
他如此努力地学英语, 好像他要去美国。
题组训练 用所给词的适当形式填空
[15] (2014 重庆, 13)It was John who broke the window. Why are you talking to me as if I had done (do)it?
[16] He speaks Chinese as fluently as if he were (be) a Chinese.
[17]Looking round the town, he felt as though he had been (be) away for ages.
(四)虚拟语气在定语从句和状语从句中的运用
1. 在定语从句中
It is(high)time(that)... 句型中, 定语从句的谓语动词用一般过去时, 或用“should + 动词原形”(其中should 不能省略)。此句型意为“(现在)该……”, 用来表示提建议。
It is(high)time that you went to school.
你该去上学了。
It is(high)time that we should start out.
我们该出发了。
2. 在目的状语从句中
在in case, for fear that, in order that, so that 等引导的目的状语从句中, 动词用“could/should/might/would + 动词原形”, 表示虚拟。
They left early for fear that they would meet him.
他们动身很早以免和他碰面。
But I gave you a map so that you wouldn't get lost!
但我怕你迷路, 给过你一张地图!
