什么情况下用不定式 急！！！
不定式在句子中可做主语、宾语、表语、定语、状语和宾语补语。
1)不定式做主语一般表示具体的某次动作。
【例如】
To complete the 30�storied building in one year was quite a difficult task.
To do that implies taking responsibility.
当主语较长，谓语较短时，常用it做形式主语，而将不定式放到谓语的后面。
【例如】
It is important for modern young people to master at least two foreign languages.
It做形式主语，不定式放在谓语动词之后常用于下列结构中：
a) It is＋形容词(easy, important, difficult, foolish, inconvenient, unnecessary, right, wrong...)＋( for/of sb.)＋不定式
【例如】
It is essential to reserve a table in advance of Christmas Eve.
It is hard to put my hopessintoswords.
It is not easy to catch fish with your hands only.
It is important for us young people to learn English and master it.
b) It is＋名词(a pleasure, a pity, a pleasant thing, one's du�ty, an honor, a shame, a crime, no easy job...)＋不定式
It is a sheer waste of time to read that kind of trash.
It is a pity to have to go without her.
It is a glorious death to die for the people.
c) It takes (sb.) some time (hours, months, days, a lot of time, patience...)＋不定式
It takes me three hours to learn English each day.
It took them half the night to get home in the snow.
2)不定式作表语不定式作表语常表示将来的动作，主语常常是表示意向、打算、计划的词，如wish, idea, task, purpose, duty, job等。
【例如】
The most important thing for one's health is to have plenty of exercise.
My chief purpose has been to point out the difficulties of the matter.
The purpose of the organization is to greet all new comers to the city and to provide them with any necessary information.
What I wanted was to get the work done as quickly as possible.
3)不定式作宾语不定式常在下列动词后面作宾语：
afford,agree,apply,arrange,ask,attempt,beg,begin,care,choose,claim,consent,demand,decide,desire,determine,expect,fail,hope,hesitate,hate,intend,learn,like,manage,mean,neglect,offer,plan,prepare pretend,promise,refuse,resolve,seek,tend,threaten,want等。
【例如】
I like to go out for walks in the warm sunshine in spring.
My mother hates to move from place to place, for she feels tired.I decide to work hard and get doctor's degree.
The room is designed to be my study, but now it has to be used as a bedroom for the children.
She failed to finish the assignment in time, and she was worried about it.
There is a man at the reception desk who seems very angry and I think he means( )trouble. (CET-4 1997, 1)
A) making
B) to make
C) to have made
D)shavingsmade
mean后面一般加不定式，所以A和D可以排除。根据句意，他看起来非常生气，他想找麻烦，不定式的动作还没有实施，应用一般式，因此答案为B。不定式作宾语还常用在下面结构中；主语＋动词＋it＋形容词＋不定式。
【例如】
We found it impossible to get everything ready in time. I think it important to learn English well in college.使用这种句型的常见动词有：believe, consider, declare, feel, find, guess, imagine, prove, realize, suppose, think,等。
4)“wh�word＋不定式”结构不定式前加一个疑问代词(what, which, who, whom, whose)或疑问副词(where, when, how, why)，以及连词whether构成特殊的不定式短语，其作用相当于一个从句，这样的不定式短语常在某些动词后面作宾语。
常见的可以接这种不定式短语的动词有：
know, see, decide, tell,ask,consider,discover,explain,findout,forget,guess,hear,imagine,inquire,learn,observe,perceive,remember,think,understand,wonder等。
【例如】
I couldn't decide which book to choose. I can tell youswheresto get this book.They found it hard to decide whether to go swimming next Sunday or to visit Aunt Sally in New Year.“wh�word+不定式”结构除了作宾语外，还可以在句中作主语或者表语。
【例如】
When to start the program remains undecided. The question is how to put the plansintospractice.
5)不定式作状语
a)不定式作状语表示目的。或用于so as和in order之后，来强调这种目的。
【例如】
To learn a foreign language well, you must make painstaking efforts.
Mother saved every cent she could spare to pay for my schooling.We must develop science and technology at high speed so as to raise scientific and cultural level of our country.
Insgroupsto get a high mark in Band 4, he did a lot of exercises both in grammar and reading comprehension.
b)不定式表示结果，特别是在so...as to, such...as to, only to...以及too...to等结构中的不定式表示结果。
【例如】
I rushed to the station as fast as I could, only to find the train already gone.
She left her hometown with her beloved man, never to return.No one is too old to learn.
Would you be so kind as to carry the luggage for me?
c)不定式常用来修饰形容词，构成下列词组：be able to, be afraid to, be apt to, be bound to, be certain to, be easy to, be eager to, be fit to, be likely to, be ready to, be sure to, be unable to, be unwilling to, be willing to等。
【例如】
Chinese team is bound to win the World Cup.
It is likely to rain today, for it is very cloudy.
I am willing to help you with your homework, for we are friends.
6)不定式作宾语补语不定式常跟在下列动词之后作宾语补语：ask, advise, allow, beg, cause, compel, command, enable, encourage, expect, feel, force, find, hear, have, inform, invite, let, make, mean, notice, order, permit, persuade, remind, require, request, teach, tell, urge, watch, warn, watch等。
【例如】
Because of the complexity of the modern equipments, most offices require secretaries to have specified training.
He asked you to call him at ten o'clock.
The note reminds me to be careful whatever I do.
I'd never allow my children to behave like that.
当不定式在let, make, have, hear, look at, listen to, feel, observe, watch, notice, perceive(感觉到)等动词后面作宾语补语时，不定式不带to.
【例如】
Whenever something is wrong with you, please do let me know.
I will have the students write a passage about Internet.
I saw my mother shed tears at the news that the neighbor girl got seriously hurt in a car accident.
It seemed so long before he heard the stone hit the water.
7)不定式作主补带有宾语及宾语补足语结构的动词变为被动语态时，原来的宾语变为主语，宾补则变为主补。加主补的动词主要有：assume, believe, know, report, say, suppose等。
【例如】
Mr. Brown is said to have left for Italy last week.(It is said that Mr. Brown left for Italy last week.)
Persons have been said to climb on roofs, solve mathematical problems, compose music, walk through windows and commit murder in their sleep.
He is reported to have won the 100�meter running race in the Olympic games.
8)不定式作定语
a)不定式作定语通常要放在其所修饰的名词或代词之后。
不定式常作下列的名词定语：attempt, ability, anything, chance, desire, determination, decision, effort, failure, intention, need, opportunity, plan, promise, pressure, right, tendency, time, way等。
【例如】
His efforts to carry out the plan were successful.I have no intention to go to the cinema with you.
There is no need to bother him with such trifles.
There is a tendency to writer quite long sentences in commercial correspondence.
The pressure( )causes Americans to be energetic, but it also put them under a constant emotional strain. (CET-4 1997,6)
A) to compete
B) competing
C) to be competed
D)shavingscompeted
pressure后面应接后置定语，表示竞争的压力。单个分词作定语一般置于名词前，故B和D可以排除。C为不定式的被动式，而竞争和压力之间没有被动关系，因此正确答案为A。
特别注意的是在不定式与其修饰的名词有动宾关系时，要根据句子的需要在不定式后加适当的介词，这个介词的选用取决于被修饰的名词或不定式本身的要求。
【例如】
She is a very nice person to work with.
This is an important issue to talk about.
b)由only, last, next,序数词或形容词最高级修饰的名词常用不定式作定语。
【例如】
Mr. Zhang is always the first man to arrive at the office and the last man to leave.I don't think he is the best one to do the work.
9)不带to的不定式在下列词组后面的不定式不带to：would rather ...than(宁愿……也不), had better...(最好)，can't help but...(不得不), had rather...(宁愿)，cannot but...(不得不，必然)，may/might as well...(不妨)，let alone(更不用说)。
【例如】
You'd better return the books to the library on time. Otherwise, you will be fined.
I can't help but wish that nothing would go wrong.
They had never seen such delicious food, let alone eat it.
在英语中，用到动词不定式的情况有很多：
在语法中，动词不定式是指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。不定式属于非谓语动词。
如果动词不定式的逻辑主语是这个不定式所表示的动作的承受者，不定式一般要用被动语态形式。如：
It's a great honour to be invited to Mary's birthday party.不定式作主语是被动语态to be invited是被邀请
It was impossible for lost time to be made up.不定式作主语
I wish to be sent to work in the country.不定式作宾语
Can you tell me which is the car to be repaired?不定式作定语
He went to the hospital to be examined.不定式作状语
在There be结构中，修饰主语的不定式可用被动，也可用主动如：There are still many things to take care of (to be taken care of).但有时两种形式表达的意思不同，如：There is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)
形式
1) 现在式：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.
I hope to see you again. = I hope that I'll see you again. 我希望再见到你。
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.
He seems to have caught a cold.
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.
完成进行式：
She is known to have been wreaking on the problem for many years.
一般在表示情绪的动词后加to do也表将来
疑问词
疑问词who,what,which,when,where,whether,how后可接不定式构成不定式短语，在句中作主语、宾语、表 语等。如：
When to leave for London has not been decided yet. 不定式在句子中做主语Mr. Smith didn't know whether to leave or stay there. 不定式在句子中做宾语
I asked Professor Xu how to learn English well. 不定式在句子中做直接宾语
The question was where to get the medicine needed. 不定式在句子中表语）
以上例句中疑问词+不定式部分，均可转换为相应的从句形式。如：When we shall leave…③…how I could learn……
经常在这种结构中使用的动词有：consider,decide,discover,explain,find out,forget,hear,know,learn,observe,understand,wonder等。
作主语
动词不定式作主语时，句子的谓语动词常用单数，其位置有以下两种：
把不定式置于句首。如：
To get there by bike will take us half an hour.
骑自行车到那儿将花费我们半个小时。
To make up for lost time is not possible.
要弥补失去的时光是不可能的。
To lean out of the window is dangerous.
身子探出窗外很危险。
To save money now seems impossible.
现在好像不可能存钱。
用it作形式主语，把真正的主语不定式置于句后，常用于下列句式中。如：
It+be+名词+to do
It's our duty to take good care of the old.
照顾老人是我们的责任。
It takes sb+some time+to do
How long did it take you to finish the work?
你花了多少时间来完成这项工作？
It+be+形容词+for sb+to do
It is difficult for us to finish writing the composition in a quarter of an hour.
我们难以在四分之一小时内完成这篇作文。
It is stupid of you to write down everything (that) the teacher says.
你把老师说的所有东西都记下来的行为是很愚蠢的。
It is an offence to drop litter in the street.在
马路上乱丢废物是违章的。
It seems(appears)+形容词+to do
It seemed impossible to save money.
在句型③中，常用表示客观情况的形容词，如：difficult,easy,hard,important,impossible,necessary 等；
在句型④中，常用careless,clever,good,foolish,honest,kind,lazy,nice,right,silly,stupid,wise等 表示赞扬或批评的词。
在不定式前的sb，可看作其逻辑主语。这一句式有时相当于Sb is+形容词+to do句式 ，如：It's kind of you to help me with my English.=You are kind to help me with my English.
It + 不定式结构可位于believe/consider/discover/expect/find/think和wonder之后
He thought it would be safer to go by train.
他认为乘火车比较安全。
He will find it is hard to make friends.
他会感觉到交朋友困难。
不定式的完成式也可作句子的主语
eg：
To have made the same mistake twice was unforgivable.
两次犯同样的错误是不可原谅的。
It is better to have loved and lost than never to have loved at all.
爱过而后失去了爱，比从未爱过要好。
不定式作为句子成分时，动词用单数形式。
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. 眼见为实
It is to believe to see.
作宾语
以下动词后，只能跟不定式作宾语
afford （付得起），agree（同意），aim(力求做到)，appear（显得），arrange（安排），ask（要求），attempt （试图），care（想要），choose（决定），claim（声称），condescend（屈尊），consent（准许），decide（决定），demand（要求），determine（决心），endeavor（竭力），expect（期待），fail（未履行），help（帮助），hesitate（犹豫），hope（希望），learn（学会），manage（设法），neglect（疏忽），offer（主动提出），plan（计划），prepare（准备），pretend（假装），proceed（接着做），promise（答应），prove（证明），refuse（拒绝），resolve（解决），seem（觉得好像），swear（发誓），tend（往往会），threaten（预示），undertake（承诺），volunteer（自愿做），vow（发誓），want（想要），wish（希望）
eg：
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。
动词+疑问词+ 不定式
decide,know,consider forget,learn,remember,show,understand,see,wonder,hear,find out,explain,tell
eg：
Please show us how to do that. 请演示给我们如何去做。
There are so many kinds of tape recorders on sale that I can't make up my mind which to bu.有这么多的录音机，我都拿不定主意买哪一种。
注意：疑问词带不定式在句中作成分时，谓语动词用单数。
The question is how to put it into practice.
问题是怎样把它付诸实施。
3)当复合宾语中的宾语是不定式时，先用形式宾语it代替不定式，把不定式置于补语之后，即：主语+动词+it+补语+to do句式。如：
We think it quite important for us to learn a foreign language well.
He feels it his duty to help the poor.
I find it difficult to learn English well.
作补语
动词+宾语+不定式(to do)
advise allow believe cause challenge compel declare encourage forbid force find hire induce instruct invite like order permit persuade remind request require select send suppose tell train urge
eg:
Father will not allow us to play on the street.
父亲不让我们在街上玩耍。
We believe him to be guilty.
我们相信他是有罪的。
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
eg:
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。
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…
eg:
The book is believed to be uninteresting.
人们认为这本书没什么意思。
there be+不定式
believe,expect,intend,like,love,mean,prefer,want,wish,undrstand
eg:
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.
eg:
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。
秃头不定式作补语
秃头不定式， 即不带“to”的不定式，其语法功能一般在句子中作宾语的补语（宾语补足语）。用秃头不定式作宾语补足语的常用动词如下：
口诀：“五看、三使役“，“两听、一感”要记住，若是“宾补”变“主补”，主补“to”字不能无。动词let属例外，其宾补/主补“to”均无。说明：
五看-----see/watch/notice/observe/look at；三使役-----have/make/let；两听-----hear/listen to；一感-----feel。
eg:
I often see him go to school on foot.(秃头不定式作宾语补足语) He is often seen to go to school on foot.(不定式作主语补足语，要带“to”) Let him try again.---- He is let try again.(let的主补与宾补均用秃头不定式)
Find 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。
eg:
I found him lying on the ground.
I found it important to learn.
I found that to learn English is important.
(1）动词不定式做主语
eg: To swim with you was very enjoyable.
注：动名词和动词不定式均可以做主语和表语，但动名词表示经常性的，抽象的动作，而不定式表示特指的一次性的具体的动作。
(2）动词不定式做表语
eg: Her wish is to become a teacher.
注：表语为不定式时，主语也是不定式；当主语部分含有动词do时，做表语的不定式可以省略to.
eg: To see is to believe.
All you have to do is (to) study hard.
(3) 不定式做宾语
以下及物动词后常用动词不定式：
want,decide,aim(目标),manage(试图),hope,ask,happen,like,love,choose,prevent(阻止),promise,continue,plan,learn,fail等。
eg: I decide to look for a job.
(4) 动词不定式做定语
动词不定式做定语往往要后置，与被修饰词之间存在动宾关系、主谓关系、同位关系和修饰关系。如果动词不定式是不及物动词，应该在动词后加上适当的介词。如果被修饰词是地点、时间、方法，通常省略动词不定式后的介词。
eg: I have something to say.(动宾关系）
I was the last one to leave here.(主谓关系）
I have no wish to quarrel with you.(同位关系）
This is the best way to do that.(修饰关系）
I have nothing to worry about.(不及物动词后加介词）
I can't find a place to play (in).(省略介词in)
注：当名词用特定的定语如：frist,last,next,only等以及形容词最高级修饰时，后面用不定式修饰。
eg: He is the only person to know the truth.
(5）不定式做状语
不定式做状语主要表达结果、目的和原因。
eg: He worked day and night to play for the debts.(目的状语）
He woke up to find everyone gone.(结果状语）
We laughed to hear the news.(原因状语）
注：动词不定式与only连用时，可表出乎意料的结果。
eg: He went to seaside only to be drowned.
(6) 动词不定式做补语
eg: Allow me to introduce her to you.
祝您学习进步，更上一层楼！！！(⊙o⊙)
不定式可以做主语，表语，定语，补语等等
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幸堵同奥：[答案] 在下列情况下,一般要用不定式:①hate,like,love前有would(should)时,如:I'd like to have a cup of coffee.②当谓语动词begin,continue,start等是进行式时,如:Thestudents are starting to work on the di fficult maths problem.③begin,continue,start与...
鹿邑县15397462239： 什么时候使用动词不定式?什么时候使用动词不定式啊?(简要回答) - ？
幸堵同奥：[答案] 动词不定式由to+动词原形构成.这里的to是不定式标志,没有词义.不定式具有名词、形容词或副词的某些语法功能,又有动词的时态和语态的特点及作用. 有些动词可以用不定式作宾语,大致上有三种情况. 1)有些及物动词用不...
鹿邑县15397462239： 在哪些情况下用不定式, - ？
幸堵同奥：[答案] 定式.其否定形式为pretend not to do sth.. 3)Mrs. Smith warned her daughter ___ after drinking. A. never to drive B. to never driver C. never driving D. never drive 答案:A.warn sb to do sth...
鹿邑县15397462239： 动词不定式中的不定式是什么意思呀?在什么情况下的句子才该使用动词不定式呢?就象现在完成时一样,是表示过去完成的事情对现在产生的影响那么动词... - ？
幸堵同奥：[答案] 它是非谓语动词. 它是一种句子的结构.
鹿邑县15397462239： 动词不定式在哪种情况下使用 - ？
幸堵同奥： 动词不定式在中学英语中应用非常广泛,一方面在句中可起名词、形容词或副词的作用,同时也可在句中作主语、宾语、定语、状语和宾语补足语.动词不定式的形式一般是to +动词原形,但to有时要省去.而动词不定式在具体运用时用不用to,...
鹿邑县15397462239： 什么情况下用动词不定式?有什么巧记的规律吗?英语的动词不定式在什么情况下使用?怎样巧妙的分出该不该用动词不定式? - ？
幸堵同奥：[答案] 一、动词不定式在句子中不能充当谓语,没有人称和数的变化. 二、动词不定式是由“to+动词原形”构成(有时可以不带to... (him为逻辑主语) 2、表语:Our duty is to protect the environment. 3、动词宾语:此种情况可按固定搭配或句式去记. 例:...
鹿邑县15397462239： 什么时候用动词不定式 - ？
幸堵同奥：[答案] 含有带to的动词不定式句型: 1. It's time to do sth. 2. It takes sb. some time to do sth. 3. tell/ask/want/encourage/invite/ sb. ... 一般情况下,我们应记住三个短语:what to do、how to do it和which to choose. 4. 不定式的逻辑主语:不定式动词仍保留动词...
