语法讲座之不定式
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基本概念
1.不定式的构成
不定式是由不定式符号to+动词原形构成，在某些情况下to也可省略。
不定式一般有时式和语态的变化，通常有下表中的几种形式（以do为例）：
主动式 被动式
一般式 to do to be done
完成式 to have done to have been done
进行式 to be doing /
完成进行式 to have been doing /
1)不定式的一般式
不定式的一般式所表示的动作通常与主要谓语的动作同时或几乎同时发生，或是在它之后发生。如：
They invited us to go there this summer. 他们邀请我们今年夏天去那儿。
He stood aside for me to pass. 他站到一边让我通过。
2)不定式的完成式
不定式的完成式所表示的动作在谓语所表示的动作之前发生，它在句中可作表语、状语、宾语，有时也可作主语、定语等。如：
She seemed to have heard about this matter. 她似乎已听说过这件事。
I am sorry to have kept you waiting so long. 我很抱歉让你等了这么久。
I meant to have told you about it, but I happened to have an important thing to do.
我本来想告诉你这件事的，但我碰巧有一件重要的事要做。
It has been an honor for me to have traveled so much in your country.
对我来说，在你们国家旅行这么多地方是一件很荣幸的事情。
　
3)不定式的进行式
不定式的进行式表示正在进行的与谓语动词同时发生的动作。它在句中可以用作除谓语以外的所有成分。如：
It´s nice of you to be helping us these days. 你真好，这些天一直帮我们。
He pretended to be listening to the teacher carefully. 他假装在认真地听老师讲课。
We didn´t expect you to be waiting for us here. 我们没料到你一直在这儿等我们。
4)不定式的完成进行式
如果不定式表示的动作是谓语所表示时间之前一直进行的动作，就需要用完成进行式。如：
They are said to have been working in Tibet for 20 years. 据说他们已经在西藏工作20年了。
We are happy to have been helping each other these days.我们很高兴这些天能互相帮助。
　
5)动词不定式的否定形式是由not或never加不定式构成。如：
Try not to be late again next time. 尽量下次不要再迟到。
He wished us never to meet her again. 他希望我们永远不要再见到她。
6)疑问词+动词不定式：
不定式和疑问词whether, what, which, whom, where, when, how, why等连用可以在句中起名词的作用，通常跟在tell, know, show, decide, learn, wonder, explain, advise, teach, discuss, find out等动词后面作宾语，有时也可以充当主语、表语等。如：
On hearing the news, he didn´t know whether to laugh or to cry.
听到这个消息，他不知道该哭还是该笑。
When to hold the meeting has not decided. 什么时候开会还没有决定。
The most important problem is how to get so much money.
最重要的事情是如何搞到这么多钱。
介词后一般不直接接不定式，但可以接疑问词+不定式短语作宾语。如：
Mary gave some advice on how to learn English. 玛丽提了一些如何学习英语的建议。
I have no idea of how to do it. 我不知道该怎么做。
　
7)不定式的被动式：
当不定式逻辑上的主语是这个不定式所表示的动作的承受者时，不定式一般要用被动形式，to be +过去分词和to have been +过去分词。这些形式可以用来作主语、表语、宾语、定语、状语、补语。如：
It´s a good thing for him to have been scolded by the teacher. 对他来说，被老师责备是一件好事。
They seemed to be satisfied with the result. 他们似乎对结果很满意。
He asked to be sent to work in the countryside. 他要求被派往农村工作。
She was the last person to have been mentioned at the meeting.
她是会上最后一个被提到的人。
I had to shout to be heard. 我不得不大喊才能被听到。
We don´t like our friends to be laughed at from time to time.我们不喜欢我们的朋友不时地被嘲笑。
2.不定式的语法作用
1)不定式作主语：
To see once is better than to hear a hundred times. 百闻不如一见。
To master a foreign language is not an easy thing. 掌握一门外语不是一件容易的事。
在很多情况下，人们通常用it作为形式上的主语，而把不定式短语移到谓语之后，使句子显得平稳一些。如：
It´s good manners to wait in line. 排队等候是很有礼貌的。
It made us very angry to hear him speak to his mother like that. 听到他那样跟他妈妈说话我们很生气。
2)不定式作表语：
The most important thing is to put theory into practice. 最重要的事情是把理论付诸实践。
The greatest happiness is to work for the happiness of all. 最大的幸福就是为大家的幸福而工作。
3)不定式作宾语：
He wanted to know the truth. 他想知道真相。
I prefer to be starved to death rather than beg. 我宁愿被饿死也不愿乞讨。
He pretended to have read the book when I asked him about it.
我问到他的时候，他假装读过这本书。
另外，不定式在某些复合宾语中作宾语时，人们常常用it代表不定式，而将真实宾语放在补足语之后。如：
Do you think it better to translate it in this way? 你认为这样翻译是不是更好？
I feel it a great honor to be invited to speak at the meeting before so many students.
我觉得被邀请在会上面对这么多学生发言是一件很光荣的事情。
4)不定式作补语：
①不定式可以和名词或代词一起构成复合结构作动词的宾语，这时不定式被称为宾语补足语。如：
I would like you to help me with my English exercises.我想请你帮我做英语练习。
I never expected the shoes to be worn out so soon.我从来没想到鞋子这么快就穿破了。
注意：动词help后面接不定式作宾语或宾语补足语可以带to也可以不带to。如：
Who can help me (to) carry this heavy box? 谁能帮我拎这个重箱子？
②在make, let, have等使役动词和see, watch, notice, hear, feel等感官动词后的复合宾语中，动词不定式不带to。
I often hear her sing in the next room. 我经常听到她在隔壁唱歌。
They make the baby go to bed at 7:00 p.m. every day.他们每天让孩子晚上7：00上床睡觉。
注意：get, leave等词也有“让”“叫”的意思，和使役动词意思相近，但它们后面的不定式作宾语补足语必须要有to。如：
I´ll get him to try it again.我将让他再试一次。
How could you leave him to have supper with a stranger? 你怎么让他跟一个陌生人一起吃晚饭？
注意：当使役动词和感官动词变为被动语态时，不定式就成了主语补语，作主语补语的不定式必须加to。如：
Though he had often made his little sister cry, today he was made to cry by his little sister. 尽管他经常弄哭他的小妹妹，但今天他却被他的小妹妹弄哭了。
He is often heard to sing the song. 经常有人听到他唱这首歌。
③think, consider, believe, declare, suppose, find, imagine, know, understand, take, prove, feel等动词后面接的不定式短语作补语多由to be+形容词或名词构成，think, consider, find后的to be常可省略。如：
When he woke up, she found herself (to be ) badly injured.她醒来的时候，发现自己受了重伤。
I thought her (to be) nice and honest the first time I met her.我第一次见到她的时候就认为她人很好，很诚实。
含有此类复合宾语的句子变成被动语态时，不定式同样被称之为主语补足语。如：
The young man was considered to have great promise.这个年轻人被认为大有前途。
The situation was found to be quite encouraging.形势看来很使人鼓舞。
④以be said, be reported, be known, seem, happen, prove, appear等构成谓语的句子中，动词不定式通常也可看作主语补语。如：
More than 20 people were reported to have been killed in the accident.
据报道，有20多个人死于事故。
I happened to be talking with him when he was hit by a car. 他被汽车撞的时候，我碰巧在和他谈话。
5)不定式作定语：
不定式在句中作定语通常放在其所修饰的名词或代词之后，以下几种情况常用不定式作定语：
①能带不定式作宾语的动词，其同源名词可以带不定式作定语，常见的有attempt, decision, promise, plan, intention, failure, wish, determination等。如：
He hasn´t kept his promise to write to his parents regularly.他没有遵守诺言定期给他父母亲写信。
My wish to be a teacher is quite understandable. 我想成为一个教师的愿望是可以理解的。
②常与不定式搭配的形容词，其同源名词一般可以带不定式作定语，常见的有ability, anxiety, eagerness, ambition等。如：
His eagerness to finish his work in time was quite obvious.他急切地想准时完成工作是很明显的。
We admire his ability to speak a foreign language so well.
我们欣赏他能把一门外语说得这么好。
③序数词、形容词最高级或被only, last, next等词修饰的名词可以用不定式作定语。如：
He is always the first person to come and the last one to leave.他总是第一个来最后一个离开。
The next person to attend the meeting is Dr. Baker.下一个出席会议的人是贝克先生。
④还有一些名词经常带不定式作定语。如：person, man, thing, something, anything, nothing, time, way, reason, chance, courage, opportunity等。如：
We students should have the courage to face any difficulty.
我们学生应该有勇气面对任何困难。
He had no reason to leave his friends and live alone on the island.
他没有理由离开他的朋友独自住到岛上去。
⑤不定式作定语时，有时与被修饰的名词之间有意义上的动宾关系，如果该不定式动词是不及物动词，它后面需加上适当的介词。如：
There is nothing to worry about.没什么可担心的。
There are many interesting books to choose from, but I don´t know which to borrow. 有很多有趣的书可以挑选，但我不知道该借哪一本。
6) 不定式作状语：
不定式作状语可以表示行为的目的、结果、原因、条件等。
① 不定式作目的状语，有时也可以用in order (not) to, so as (not) to结构。如：
In order to protect the young plants from the sun, Mother put them in the shade.
为了保护幼苗不被太阳晒坏，妈妈把它们放到了阴凉处。
He got up very early this morning so as not to be late for school again.
今天早上他起身很早以免上学再迟到。
注意：so as (not) to do不可以置于句首。
②不定式作结果状语，常见的结构有too…to, enough…to, so…as to, such…as to, only to…等。如：
The question is too difficult for me to answer. 对我来说，这个问题很难回答。
He said he was clever enough to deal with it by himself.他说他足够聪明可以独自应付这件事。
Will you be so kind as to turn down the radio? 请你帮我把收音机调低一点好吗？
He woke up only to find himself in hospital. 他醒来发现自己在医院里。
注意：too…to通常表示太……而不……，但在下列句子中没有否定的意思。
She is only too glad to stay at home. 她太想留在家里了。
He is too anxious to know the examination results. 他很急切地想知道考试结果。
③不定式作原因状语，通常用来修饰表示情感、心理状态、性格等的形容词。常见的形容词有：happy, glad, lucky, fortunate, surprised, angry, anxious, ready, quick, slow, cruel, clever, frightened, shocked, sorry, eager, proud, disappointed, foolish, impatient, unwise, naughty等。如：
They are surprised to learn of his death. 得知他死亡的消息，他们很惊讶。
We are proud to be young people of new China. 成为新中国的青年，我们感到很骄傲。
另外，hard, difficult, easy, fit，comfortable等词也可以接动词不定式。这时候，作句子主语的除了是表示人的词外，还可以是表示物的词。如：
The water is not fit to drink. 这水不适合饮用。
The room is very comfortable to live in. 这个房间住起来很舒服。
注意：后两句中的不定式与句子的主语或宾语之间是动宾关系，此时如果不定式动词是不及物动词，则需要带上适当的介词。
3.不定式的复合结构
1)不定式复合结构的构成
不定式在使用时通常有自己的逻辑主语，一般可以是句子的主语或宾语，或者由物主代词暗示出来。如：
They plan to build a hotel. 他们计划建造一个酒店。
His father sent him abroad to study literature. 他父亲送他出国去学文学。
I could see her eagerness to go abroad. 我可以看出他急切地想出国。
但有时需要明确表示出不定式的逻辑主语（即不定式动作的执行者），此时一般用for/of +名词（代词）短语+不定式来构成不定式的复合结构。如：
It´s expensive for people to use electricity for cooking.人们用电做饭是很昂贵的。
It´s careless of you to make such a mistake. 你犯这样的错误真是粗心。
2)不定式复合结构的语法作用
不定式的复合结构在句中可以做主语、宾语、表语、状语、定语。
①不定式的复合结构作主语、宾语，通常用it 作形式主语或形式宾语来代替不定式的复合结构。如：
It´s necessary for the goods to be packed in strong cases. 货物很有必要用坚固的箱子打包。
They thought it impossible for us to find the lost child in the darkness.他们认为我们要在黑暗中找到迷路的小孩是不可能的。
②不定式的复合结构作表语、状语、定语。如：
That´s for you to decide. 那个由你来决定。
For the test to be passed, the students should work harder than before.为了能通过考试，学生们应该比以往更认真学习。
I have some books for you to read.我有几本书送给你读。

重点疑难
1.不定式不带to的规则：
前面我们已经谈到，在一些使役动词和感官动词后的不定式作宾语补语时，不定式符号to常常省略，下面还有几种情况请大家注意：
① 动词原形come, go等在口语中可接不带to的不定式。如：
Go tell her. 去告诉他。
Come have a glass. 来喝一杯。
②在why引起的一些疑问句中，疑问词直接跟动词原形或not+动词原形。如：
Why spend so much money? 为什么花这么多钱？
Why not let her have a try? 为什么不再让她试一试？
③在had better（还是……最好）, had best（最好，顶好）, would rather（宁可，宁愿）, would rather…than（宁可……而不……）, would sooner（宁可，宁愿）, would sooner…than（宁可……而不……）, cannot but（不得不，必然）, cannot choose but（只得）, cannot help but（不得不）等结构后直接跟动词原形或not +动词原形。如：
You´d better listen to your teacher´s opinion. 你最好听一听老师的看法。
I would rather work than stay idle. 我宁愿工作而不愿闲坐。
Rather than ride on a crowded bus, he always prefers to ride a bicycle.他宁愿挤公共汽车也不愿骑自行车。
Liu Hulan would sooner die than surrender.刘胡兰宁死不屈。
One´s world outlook cannot but come through in what one says and does.
一个人的世界观必然在他的言行中表现出来。
④在介词but, except之前如有动词do的任一形式，其后的动词不定式不用to。如：
Last evening I did nothing but repair my farm tools. 昨晚上我除了修理农具外，没有做其它的事情。
Now there was nothing he could do except admit defeat.现在他只有认输。
如but 之前没有do，其后的不定式则一般要加to。如：
I´m afraid we have no choice but to take a taxi.恐怕我们别无选择，只好乘出租车了。
They desired nothing but to succeed.他们只想成功。
⑤在出现并列的动词不定式时，为了避免重复，后面的不定式符号to可省略。如：
I really don´t know what to say and do. 我真的不知道该说什么，该干什么。
Can you help me to call him and ask him to attend the meeting at 2:00 p.m.?你能不能帮我打电话给他，叫他下午两点来开会？
但如果两个不定式有对比的意思，则不定式符号to不可被省去。如：
I came not to scold you but to praise you. 我是来夸你的，不是来骂你的。
The purpose of the new technology is to make life easier, not to make it more difficult.新技术的目的是为了使生活更容易，而不是使生活更艰难。
2.动词不定式的省略问题：
上文中出现了某一动词或动词短语，下文中再遇到此动词的不定式结构时，往往要省略动词不定式，但通常省略动词原形或短语而保留不定式符号to，一般有下面几种情况：
①含有助动词或情态动词如be going to, used to, have to, ought to, be able to, be about to等+动词原形结构时：
---Do you think I ought to go to see my doctor? 你认为我应该去看医生吗？
---Yes, I think you ought to. 是的，我想你应该去。
She must go but you don´t have to. 她必须走，但你没有必要。
②含有动词want, decide, like, love, hope, wish, mean, refuse, try等+不定式作宾语结构时：
---Did you go to see the Great Wall? 你去看长城了吗？
---I wanted to, but I was too busy. 我本来想去的，但我太忙了。
You may go with them if you hope to. 如果你希望的话，你可以和他们一起去。
③含有动词如ask, tell, order, advise, persuade, warn, wish, permit, allow, forbid等+不定式做宾语补语或主语补语时：
Don´t do anything unless your father tells you to. 除非你父亲叫你去做，不然不要做任何事情。
---May I use your car? 我可以用你的汽车吗？
---No, I forbid you to. 不，我禁止你使用。
④对话的答语中含有形容词如happy, glad, eager, anxious, willing, ready, pleased, afraid等+不定式作表语结构时：
---Will you lend me a hand? 你能帮我一个忙吗？
---I´m willing to, but I can´t now. 我很愿意，但我现在不行。
---Would you please come to my birthday party tomorrow? 明天下午来参加我的生日聚会好吗？
---I´ll be glad to. 我很乐意。
3.不定式主动语态和被动语态的区别：
动词不定式在句中究竟用主动还是被动，有时比较复杂。主要有下面几种情况：
①不定式所修饰的名词或代词和不定式逻辑上构成主谓关系时，不定式往往用主动形式。如：
Have you got a key to unlock the door? 你有开门的钥匙吗？
②不定式做后置定语，和被修饰名词或代词构成逻辑上的动宾关系，又和该句主语构成逻辑上的主谓关系时，不定式常用主动形式，不定式为不及物动词时，其后应加相应的介词。如：
Do you have anything to say on this question? 针对这个问题你还有什么要说的吗？
He is a pleasant person to work with. 他是一个合作愉快的人。
③不定式作表语形容词的状语，和句子主语构成逻辑上的动宾关系时，不定式多用主动形式，不定式为不及物动词时要加相应的介词。如：
The fish is delicious to eat. 这鱼很好吃。
The chair is comfortable to sit on. 这把椅子坐起来很舒服。
④在There be结构中，当说话人考虑的是必须有人去完成某件事时，不定式用主动形式；如果说话人强调的是事情本身必须完成，则用被动形式。如：
There is nothing to worry about. 没什么可担心的。
There is a lot of work to do. 有许多事情要做。（表示某人必须做这工作）
注意下面两个句子的含义：
There is a lot of work to be done. （强调有许多事情必须做。）
There is nothing to be done. （强调出了某事，现在没办法解决。）
4.for somebody to do和of somebody to do的用法区别：
句型“It is +形容词+for somebody+不定式”中的形容词通常强调不定式的行为属性，如：important, possible, impossible, necessary, difficult, hard, reasonable等。
It´s difficult for us to finish the work within two hours. 我们要在两小时之内完成工作是很难的。
It´s reasonable for them to run away so quickly. 他们这么快就逃跑了是很有道理的。
“It is +形容词+of somebody+不定式”中的形容词表示人物性格和特征。如：kind, silly, good, unwise, clever, wrong, right, foolish, stupid, careless, rude, impolite, bold, thoughtful, honest, bad, sensible, naughty等。
It´s kind of you to think so much of us. 难为你这么为我们着想。
It´s silly of the boy to keep pouring water into the basket 这个男孩真傻，一直往篮子里倒水。
5.高中阶段能接不定式的常见动词：
能接不定式作宾语的常见动词有：want（想要）, like（喜欢）, wish（希望）, hate（憎恨，讨厌）, prefer（宁愿）, hope（希望）, fail（失败）, plan（计划）, refuse（拒绝）, ask（要求）,continue（继续），manage（设法）, try（尽力）, offer（提供）, start（开始）, begin（开始）, forget（忘记）, remember（记得）, promise（答应）, mean（打算）, pretend（假装）, intend（想，打算）, attempt（尝试，企图）, decide（决定）, learn（学会）, desire（渴望，请求）, agree（同意）, care（关心，喜欢）, choose（选择）, determine（下决心）, expect（期望）, afford（负担得起，买得起）等。
能接不定式做补语的常见的动词有：感官动词see, watch, notice, hear, feel等；使役动词make, let, have 等；还有一般的动词如advise（建议）, allow（允许）, ask, beg（乞求）, command（命令，指挥）, tell（告诉）, invite（邀请）, force（强迫）, oblige（强迫）, get（致使）, help（帮助）, wish, want, like, hate, prefer, intend, expect, encourage（鼓励）, persuade（说服）, permit（允许，许可）, remind（使想起，提醒）, request（请求，要求）, order（命令）, warn（警告，提醒）, cause（引起）等。
6.高中阶段常见的不定式短语：
高中阶段常见的一些不定式短语可以作谓语，如：be able to do（能，会）, be about to do（即将做……）, used to do（过去常常……）, be glad to do（乐意做……）, would like to do（想要做……）,be likely to do（很可能做……）, go all out to do something全力以赴,be supposed to do应该等。
高中阶段还有一些不定式短语可以作状语修饰整个句子，也可以称它们为插入语。如：to tell you the truth（说老实话），to be frank（坦率地说）, to begin with（首先）, to be brief（简言之）, to make a long story short（长话短说）, to be exact（精确地说）, to say nothing of（姑且不说），to conclude（总而言之）, to be sure（诚然、固然）， to do him justice（说句对他公道的话）,so to speak（可以这么说、打个譬喻说）等。
To tell you the truth, I hate him. 说老实话，我恨他。
To be frank, I don´t agree with what you said. 坦率地说，我不同意你说的话。

专项练习
Ⅰ. 选择填空：
1. I´ve heard him ______ about you often.
A. speak B. speaks C. spoke D. speaking
2. I went to see him, _______ him out.
A. finding B. find C. only to find D. to finding
3. He didn´t know _______ or stay.
A. to leave B. if that he should leave C. if to leave D. whether to leave
4. ---Will the Smiths go abroad this summer?
---No, they finally decided _______ .
A. to B. not going C. not to D. not to be going
5. ---I usually go there by train. ---Why not _______ by boat for a change.
A. to try going B. trying to go C. to try and go D. try going
6. He pretended _______ nothing about it.
A. know B. to know C. knowing D. knew
7. Little Jim should love _______ to the theatre this evening.
A. to be taken B. to take C. being taken D. taking
8. They would not allow him _______ across the enemy line.
A. to risk going B. risking to going C. for risk to go D. risk going
9. There are so many kinds of tape-recorders on sale that I can´t make up my mind _______ to buy.
A. what B. which C. how D. where
10. Charles Babbage is generally considered _______ the first computer.
A. to invent B. inventing C. to have invented D. having invented
11. The missing boys were last seen _______ near the river.
A. playing B. to be playing C. play D. to play
12. The patient was warned _______ oily food after the operation.
A. to eat not B. eating not C. not to eat D. not eating
13. I regret _______ you that we are unable to offer you employment.
A. informing B. having informed C. to inform D. to informing
14. You had better get a doctor _______ your bad tooth.
A. pull out B. to pull out C. pulled out D. pulling out
15. The matter had better _______ as it is.
A. leave B. being left C. leaving D. be left
16.He was so foolish _______ his car unlocked.
A. to leave B. that leave C. as to leave D. for him to leave
17. Almost everyone fails _______ the driving test on the first try.
A. passing B. to have passed C. to pass D. in passing
18. The girl was made _______ she didn´t love at all.
A. marry a man B. to marry a man C. to marry with a man D. married with a man
19. The man will use what he has _______ a camera for his wife.
A. to get B. got C. buy D bought
20. To answer correctly is more important than _______ .
A. a quick finish B. to finish quickly C. finishing quickly D. you finish quick
21. Tom kept quiet about the accident _______ lose his job.
A. so as not to B. so not as to C. so as to not D. not so as to
22. I felt it an honor _______ to speak here.
A. to ask B. asking C. to be asked D. having asked
23. ---I´d like to buy an expensive camera.
---Well, we have several models _______ .
A. to choose from B. to choose C. to be chosen D. for choice
24. _______ to the left and you´ll see the post office.
A. To turn B. Turning C. Turned D. Turn
25. Will you be able to attend the lecture next week?
A. giving B. given C. to be given D. being given
Ⅱ. 句子改错：
1. I don´t know if to help him or not.
2. She can´t help cleaning the house because she´s busy making a cake.
3. We all hope you to make rapid progress.
4. The results of the research are to publish soon.
5. It is too heavy for me to lift it.
6. It´s awfully good for you to come and meet us.
7. These are very good books for your children to be read.
8. He did what he could help me with my physics.
9. Let´s find a place to put the things.
10. It would be easier to climb over the mountain than going round the valley.
I. 选择填空：
1---5 A C D C D 6---10 B A A B C
11---15 A C C B D 16---20 C C B A B
21---25 A C A D C
II.句子改错：
1.if →whether 2.cleaning →to clean 3.hope →wish
4.publish →be published 5.lift it →lift 6.for →of
7.be read →read 8.help →to help 9.things →things in
10.going →to go

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