标题：不定式
概念
在语法中，[1]是动词的一种不带词形变化从而不指示人称、数量、时态的形式。它被叫做不定式，是因为动词不被限定，或者说不被词形变化所局限。
动词不定式指由to 加上动词原形（而且只能是动词原形）所构成的一种非限定性动词，但在有些情况下to可以省略。动词不定式在语法功能上可作主语 、宾语、表语、定语和状语。
构成形式
动词不定式可以作以上各种成分，但它毕竟是动词，所以有动词的属性。
动词不定式及其短语还可以有自己的宾语、状语，虽然动词不定式在语法上没有表面上的直接主语，但它表达的意义是动作，这一动作一定由使动者发出。这一使动者我们称之为逻辑主语，其形式如下：
时态
主动形式
被动形式
一般式
（not）to do
（not）to be done
完成式
（not）to have done
（not）to have been done
进行式
（not）to be doing
完成进行式
（not）to have been doing
1) 一般式：一般现在时表示的动词，有时与谓语动词表示的动作同时发生，有时发生在谓语动词的动作之后。
He seems to know this.他好像知道这。
I hope to see you again. = I hope that I'll see you again.　我希望再见到你。
2) 完成式：表示的动作发生在谓语动词表示的动作之前。
I'm sorry to have given you so much trouble. 很抱歉给你添了这么多麻烦。
He seems to have caught a cold. 他似乎感冒了。
3) 进行式：表示动作正在进行，与谓语动词表示的动作同时发生。
He seems to be eating something.他似乎在吃东西。
4) 完成进行式：表示动作从过去某一时间开始一直延续到现 在或离现 在不远的时间
She is known to have been wreaking on the problem for many years.她知道已处于这个问题很多年了。
句中成分
作宾语1）动词+ 不定式
afford,aim,appear,agree,arrange,ask,be,decide,bother,care,choose,come,dare,demand,desire,determine,expect,elect,endeavor,hope,fail,happen,help,hesitate,learn,long,mean,manage,offer,ought,plan,prepare,pretend,promise,refuse,seem,tend,wait,wish.　
The driver failed to see the other car in time.　
司机没能及时看见另一辆车。
I happen to know the answer to your question.　
我碰巧知道你那道问题的答案。
2）动词+宾语+不定式
ask, beg, choose, expect , hate, help intend like, love, need prefer, prepare, promise, want, wish…
例句：
a.　I like to keep everything clean.
我喜欢每件东西都保持整洁。
b.　I like you to keep everything clean.
我喜欢你能使每件东西都保持整洁。
c.　I want to talk to Tom.
我想和汤姆谈话。
d.　I want you to talk to Tom.
我想让你和汤姆谈话。
3）动词+疑问词+ 不定式
decide, know, consider forget, learn, remember, show, understand, see, wonder, hear, find out, explain, tell　
例句：
a.　Please show us how to do that.
请演示给我们如何去做。
b.　There are so many kinds of tape-recorders on sale that I can't make up my mind which to buy.
有这么多的录音机，我都拿不定主意买哪一种。
c.　The question is how to put it into practice.
问题是怎样把它付诸实施。
（注意：疑问词带不定式在句中作成分时，谓语动词用单数。）作补语1) 动词+宾语+不定式(to do)
advise,allow,appoint,believe,cause,challenge,command,compel,consider,declare,drive,enable,encourage,find,forbid,force,guess,hire,imagine,impel,induce,inform,instruct,invite,judge,know,like,order,permit,persuade,remi-nd,report,request,require,select,send,state,suppose,tell,think,train,trust,understand,urge,warn…
例句：
a.　Father will not allow us to play on the street.　
父亲不让我们在街上玩耍。
b.　We believe him to be guilty.
我们相信他是有罪的。
Find 的特殊用法：
Find 后可用分词做宾补，或先加形式宾语，再加形容词，最后加带to 的动词不定式。find后也可带一个从句。此类动词还有get，have。
例句：
a.　I found him lying on the ground.
b.　I found it important to learn.
c.　I found that to learn English is important.
典型例题:
The next morning she found the man ___ in bed，dead.　
A. lying　B. lie　C. lay　D. laying　
答案：A.find的宾语后面，用分词或分词短语，起宾语补足语作用。现在分词表达主动，也表达正在进行，过去分词表达被动。
2) to + be 的不定式结构，作补语的动词
Acknowledge,believe,consider,think,declare(声称),discover,fancy(设想),feel,find,guess,judge,imagine,know,　prove,see(理解),show,suppose,take(以为),understand
例句：
a.　We consider Tom to be one of the best students in our class.
我们认为汤姆是班上最好的学生之一。
典型例题
Charles Babbage is generally considered　__ the first computer.　
A. to invent　B. inventing　C. to have invented　D. having invented　
答案：A. 由consider to dosth. 排除B、D。. 此句只说明发明这一个事实，不定式后用原形即可。而C为现在完成时，发明为点动词一般不用完成时，且此处也不强调对现 在的影响，因此不选C。
3) to be +形容词
Seem,appear,be said,be supposed,be believed,be thought,be known,be reported,hope, wish,desire,want,plan,expect,mean…
例句：
a.　The book is believed to be uninteresting.
人们认为这本书没什么意思。
4)　there be+不定式
believe,expect,intend,like,love,mean,prefer,want,wish,undrstand
例句：
a.　We didn't expect there to be so many people there.
我们没料到会有那么多人在哪里。
有些动词需用as 短语做补语，如regard, think believe, take, consider.
We regard Tom as our best teacher.　我们认为汤姆是我们最好的老师。
Mary took him as her father .　玛丽把他当作自己的父亲。作主语easy,difficult,hard,important,possible,impossible,comfortable,necessary,better;　
the first,the next,the last,the best,too much,too little,not enough,Kind,nice,stupid,rude,clever,foolish,thoughtful,thoughtless,brave,considerate,silly,elfish
例句：
a.　It's easy (for me) to do that.
我做这事太容易了
b.　It's so nice to hear your voice.
听到你的声音真高兴。
b.　It's necessary for you to lock the car when you do not use it.
当你不用车的时候，锁车是有必要的。
c.　It's very kind of him to help us.
他帮助我们，他真好。
d.　It was silly of us to believe him.
我们真愚蠢，竟然相信了他。
e.　It seemed selfish of him not to give them anything.
他不给他们任何东西，这显得太自私了。
注意：
1) 其他系动词如，look，appear等也可用于此句型。
2) 不定式作为句子成分时，动词用单数形式。
3) 当不定式作主语的句子中又有一个不定式作表语时，不能用It is… to…的句型
(对)To see is to believe.　百闻不如一见。
(错)It is to believe to see.作表语不定式可以在句中作表语，起名词的作用。
例如：My work is to clean the room every day.
His dream is to be a doctor.作定语不定式作表语表示具体动作或将来动作；动名词作表语表示抽象的一般行为。
①To be kind to the enemy is to be cruel to the people.
②My chief purpose is to point out the difficulties ofthe matter.
③What I would suggest is to put off the meeting.
当主语和表语都是不定式时，其含义一是条件，一是结果
（例①）。当主语是aim,duty,hope,idea,mista ke,plan,purpose,suggestion等为中心词的名词词组
（例②）时，或以what引导的名词性分句
（例③），不定 式说明主语的内容。
（例④）Our work is serving the people.
（例⑤）What he likes is taking a walk after supper.
（例⑥）The story told by Mr.Wang is interesting.
④⑤句动名词作表语，与主语部分可以转换，如Serving thepeople is out work,而⑥句中是现在分词作表语，说明主语的性质、状态，现在分词具有形容词的各种特征，另外，动名词作表语还应与进行时态区别开来。作状语1）目的状语
To… only to,in order to,so as to, so (such)… as to…　
例句：
①He ran so fast as to catch the first bus.
他飞快地跑以便赶上第一班车。
②I come here only to say good-bye to you.
我来仅仅是向你告别。
2）作结果状语，表事先没有预料到的，要放在句子后面。
①What have I said to make you angry.
②He searched the room only to find nothing.
3）表原因
I'm glad to see you.
典型例题
The chair looks rather hard, but in fact it is very comfortable to ___.
A. sit　B. sit on　C. be seat　D. be sat on
答案：B.如果不定式为不及物动词，其后应有必要的介词。当动词与介词连用时，常位于"形容词+动词不定式"结构的末尾。
特殊句型
1、so as to
1） 表示目的；它的否定式是so as not to do。
Tom kept quiet about the accident so as not to lose his job.
汤姆对事故保持沉默是为了不丢掉他的工作。
Go in quietly so as not to wake the baby.
轻点进去，别惊醒了婴儿。
2)　so kind as to ---劳驾
Would you be so kind as to tell me the time?
劳驾，现在几点了。
2、 "Why not +动词原形"表达向某人提出建议
"为什么不……?" "干吗不……?"
例如：
Why not take a holiday?
干吗不去度假?
3、It's for sb.和 It's of sb.
1）for sb. 常用于表示事物的特征特点，表示客观形式的形容词，如easy, hard, difficult,　interesting, impossible等：
It's very hard for him to study two languages. 对他来说学两门外语是很难的。
2）of sb的句型一般用表示人物的性格，品德，表示主观感情或态度的形容词，如good, kind, nice, clever, foolish, right。
It's very nice of you to help me. 你来帮助我，你真是太好了。
for 与of 的辨别方法：
用介词后面的代词作主语，用介词前边的形容词作表语，造个句子。如果道理上通顺用of，不通则用for。如：
You are nice.　(通顺，所以应用of)。
He is hard.　(人是困难的，不通，因此应用for。)
4、不定式的特殊句型too…to…
1）too…to　太…以至于…
He is too excited to speak.
他太激动了，说不出话来。
---- Can I help you ? 需要我帮忙吗?
---- Well, I'm afraid the box is too heavy for you to carry it, but thank you all the same.　不用了。这箱子太重，恐怕你搬不动。谢谢您。
2) 如在too前有否定词，则整个句子用否定词表达肯定， too 后那个词表达一种委婉含义，意 为"不太"。
It's never too late to mend.　(谚语)
改过不嫌晚。（亡羊补牢，为时不晚）
3)　当too 前面有only, all, but时，意思是：非常… 等于very。
I'm only too pleased to be able to help you. 我非常高兴能帮助你。
He was but too eager to get home. 他非常想回家。1） 动名词与不定式的区别：　
动名词表达的是： 状态，性质，心境，抽象，经常性，已发生的　不定式表达的是： 目的，结果，原因，具体，一次性，将发生的
2）接不定式或动名词，意义相同。
3）动名词与不定式语义不同的有11 组：　
1 stop to do　stop doing　
2 forget to do　forget doing
3 remember to do　remember doing　
4 regret to do　regret doing
5 cease to do　cease doing　
6 try to do　try doing
7 go on to do　go on doing　
8 afraid to do　afraid doing
9 interested to do　interested doing　
10 mean to do　mean doing
11 begin/ start to do　begin/ start doing
1 forget doing/to do
forget to do　忘记要去做某事。　(未做)
forget doing　忘记做过某事。　(已做)
The light in the office is stil on. He forgot to turn it off.
办公室的灯还在亮着，它忘记关了。(没有做关灯的动作)
He forgot turning the light off.
他忘记他已经关了灯了。　( 已做过关灯的动作)
Don't forget to come tomorrow.
别忘了明天来。　(to come动作未做)
典型例题
---- The light in the office is still on.
---- Oh，I forgot___.　
A. turning it off　B. turn it off　C. to turn it off　D. having turned
it off
答案：C。由the light is still on 可知灯亮着，即关灯的动作没有发生，因此用forget to do sth.
而forget doing sth表示灯已经关上了，而自己忘记了这一事实。此处不符合题意。
2 stop doing/to do
stop to do　停止，中断做某事后去做另一件事。
stop doing　停止做某事。
They stop to smoke a cigarette.　他们停下来，抽了根烟。
I must stop smoking..　我必须戒烟了。
典型例题
She reached the top of the hill and stopped ___　on a big rock by the
side of the path.　
A. to have rested　B. resting　C. to rest　D. rest
答案：C。由题意可知，她到了山顶，停下来在一个路边的大石头上休息。因此，应选择"stop to do sth.
停下来去做另一件事"。而不仅仅是爬山动作的终止，所以stop doing sth.不正确。
3 remember doing/to do
remember to do 记得去做某事　(未做)
remember doing　记得做过某事　(已做)
Remember to go to the post office after school.
记着放学后去趟邮局。
Don't you remember seeing the man before?
你不记得以前见过那个人吗?
4 regret doing/to do
regret to do　对要做的事遗憾。　(未做)
regret doing　对做过的事遗憾、后悔。　(已做)
I regret to have to do this, but I have no choice.
我很遗憾必须这样去做，我实在没有办法。
I don't regret telling her what I thought.　
我不为告诉她我的想法而后悔。
典型例题
---You were brave enough to raise objections at the meeting.
---Well, now I regret ___ that.
A. to do　B. to be doing　C.　to have done　D.　having done
答案：D。regret having done sth. 对已发生的事感到遗憾。regret to do sth.
对将要做的事感到遗憾。本题为对已说的话感到后悔，因此选D。
5 cease doing/to do
cease to do　长时间，甚至永远停做某事。
cease doing　短时停止做某事，以后还会接着做。
That department has ceased to exist forever.
那个部门已不复存在。
The girls ceased chatting for a moment when their teacher passed by.
姑娘们在老师走过时，停止了聊天。
6 try doing/to do
try to do　努力，企图做某事。
try doing　试验，试着做某事。
You must try to be more careful.
你可要多加小心。
I tried gardening but didn't succeed.
我试着种果木花卉，但未成功。
7 go on doing/to do
go on to do　做了一件事后，接着做另一件事。
go on doing　继续做原来做的事。
After he had finished his maths，he went on to do his physics.
做完数学后，他接着去做物理。
Go on doing the other exercise after you have finished this one.
作完这个练习后，接着做其他的练习
8 be afraid doing/to do
be afraid to do　不敢，胆怯去做某事，是主观上的原因不去做，意为"怕"；
be afraid of doing　担心出现doing的状况、结果。 doing 是客观上造成的，意为"生怕，恐怕"。
She was afraid to step further in grass because she was afraid of being
bitten by a snake.
她生怕被蛇咬着，而不敢在草丛中再走一步。
She was afraid to wake her husband.
她不敢去叫醒她丈夫。
She was afraid of waking her husband.
她生怕吵醒她丈夫。
.9 be interested doing/to do
interested to do　对做某事感兴趣，想了解某事。
interested in doing　对某种想法感兴趣，doing 通常为想法。
I shall be interested to know what happens.
我很想知道发生了什么事。 (想了解)
I'm interested in working in Switzerland. Do you have any idea about that?
我对在瑞士工作感兴趣。你想过这事吗?　(一种想法)
10 mean to doing/to do
mean to do　打算、想
mean doing　意味着
I mean to go, but my father would not allow me to.
我想去，但是我父亲不肯让我去。
To raise wage means increasing purchasing power.
赠加工资意味着增加购买力。
11 begin(start) doing/to do
begin / start to do sth
begin / start doing sth.
1)　谈及一项长期活动或开始一种习惯时，使用doing.
How old were you when you first started playing the piano?
你几岁时开始弹钢琴？
2)　begin, start用进行时时，后面动词用不定式to do
I was beginning to get angry。
我开始生起气来。
3)　在attempt, intend, begin, start 后接know, understand, realize这类动词时，常用不定式to do。
I begin to understand the truth。
我开始明白真相。
4)　物作主语时
It began to melt.
12感官动词+ doing/to do
感官动词see, watch, observe, notice, look at, hear, listen to, smell, taste,
feel + do　表示动作的完整性，真实性；+doing 表示动作的连续性，进行性
I saw him work in the garden yesterday.
昨天我看见他在花园里干活了。(强调"我看见了"这个事实)
I saw him working in the garden yesterday.（强调"我见他正干活"这个动作）
昨天我见他正在花园里干活。
典型例题
1）They knew her very well. They had seen her ___ up from childhood.　
A. grow　B. grew　C. was growing　D. to grow
答案：A。因题意为，他们看着她长大，因此强调的是成长的过程，而非正在长的动作，因此用see sb do sth 的句型。
2）The missing boy was last seen ___ near the river.　
A. playing　B. to be playing　C. play　D. to play
答案A. 本题强调其动作，正在河边玩，应此用see sb. doing sth句型。
省to的动词不定式
1）情态动词( 除ought 外，ought to)：
2）使役动词let, have, make：
3）感官动词see, watch, look at, notice , observe, hear, listen to, smell, feel, find 等后作宾补，省略to。
注意：在被动语态中则to 不能省掉。
I saw him dance.
=He was seen to dance.
The boss made them work the whole night.
=They were made to work the whole night.
4） would rather，had better：
5） Why… / why not…：
6） help 可带to，也可不带to, help sb (to) do sth：
7） but和except：but前是动词do时，后面出现的动词用不带to的动词不定式。
8） 由and, or和than连接的两个不定式，第二个to 可以省去：
9） 通常在discover, imagine, suppose, think, understand等词后，可以省去to be：　
He is supposed (to be) nice.　他应该是个好人。
10）but作介词，后接不定式结构时，前面谓语动词部分若含有do的形式时，but后的不定式要省去to，否则要带to。　
He wants to do nothing but go out.
He wants to believe anything but to take the medicine.
11）当两个或多个不定时短语由连词and，but或or连接时，后一个或几个不定式符号to常省略。但若表示对比、对照关系时，则不能省略。
He wants to move to France and marry the girl.
The purpose of new technologies is to make life easier,not to make it more difficult.
12）不定式做表语时，一般要带to，但若主语部分中含有do的各种形式时，符号to可省去。
We've missed the last bus.All we could do now is walk home.
举例：
He wants to move to France and marry the girl.
He wants to do nothing but go out.
比较：He wants to do nothing but go out.
He wants to believe anything but to take the medicine.
典型例题
1)—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　
答案：D. why not 后面接不带to 的不定式，因此选D。
2） Paul doesn't have to be made ___. He always works hard.　
A. learn　B. to learn　C. learned　D. learning
答案：B. make后接不带to 的动词不定式，当其用于被动时，to 不可省略。
注意区别用作介词的to
to 有两种用法： 一为不定式+动词原形； 一为介词+名词/动名词, to 在下面的用法中是第二种，即to+ 名词/动名词：
admit to承认，confess to承认，be accustomed to 习惯于，be used to 习惯于， stick to 坚持， turn to开始，着手于， devote oneself to 献身于，　be devoted to 致力于， look forward to 盼望，pay attention to 注意
用法
一般式一、表示将来
即表示发生在谓语动作之后的动作。如：
We decided to leave early. 我们决定早点动身。
I hope to finish reading the book to night. 我希望今晚看完这本书。
I should like to give him a chance. 我愿意给他一个机会。
He asked me to buy him some paper. 他叫我给他买些纸。
We expect him to come in time. 我们希望他能及时来。
二、表示同时
表示与谓语动作同时发生的动作。如：
He seems to be tired. 他似乎累了。
注：以下用作宾语补足语的不定式省略了to：
Who heard him say that? 是谁听到他这样说的？
Did you notice me pause? 你注没注意我停顿了一下？
三、表示过去
表示略先于谓语动作的动作。如：
I’m sorry to hear that. 听到这事我很难过。(to hear 略先于am sorry)
Helen was pleased to see him.海伦见到他很高兴。
I’m happy to meet you at last. 我很高兴我终于碰到了你。
I’m glad to see you looking so happy. 我很高兴看到你显得这样快活。进行式一、表示同时
表示与谓语动作同时发生且正在进行的动作。如：
He seems to be saying something. 他似乎在说什么。
He is thought to be hiding in the woods. 人们认为他躲在林子里。
It’s nice to be sitting here with you. 和你一起坐在这儿真好。
Why’s she so late?—She can’t still be working. 她怎么这么晚还不来?——她不可能还在工作吧。
二、表示将来
正如可用进行时态表示将来意义一样，不定式的进行式有时也可表示将来。如：
He was happy to be coming home. 就要回家了他感到高兴。
The old man seems to be dying. 这老人似乎要死了。完成式一、表示发生在谓语动作之前的动作：
He seems to have caught a cold. 他似乎感冒了。
I hate to have quarreled with her. 我痛恨和她吵架。
I believe it to have been a mistake. 我相信这是一个错误。
You appear to have travelled quite a lot. 你似乎作过多次旅行。
I’m sorry to have given you so much trouble. 对不起给了你这么多麻烦。
It’s said to have been built in the Ming dynasty. 据说它是明朝修建的。
二、表示在某个给定的时间之前已完成的动作：
I hope to have finished the work by now. 我希望现 在以前已完成这项工作。
三、表示过去未曾实现的想法和愿望：
I should like to have come earlier. 我本想早点来的。
We were to have been married last year. 我们本来打算去 年结婚的。
用法汇总
(1) 一是表示将来，即表示发生在谓语动作之后的动作。如：
We decided to leave early. 我们决定早点动身。
He asked me to buy him some paper. 他叫我给他买些纸。
We expect him to come in time. 我们希望他能及时来。
(2) 表示与谓语动作同时发生或略先于谓语动作的动作。如：
He seems to be tired. 他似乎累了。
Who heard him say that? 是谁听到他这样说的?
I’m sorry to hear that. 听到这事我很难过。(to hear 略先于am sorry)[2]