不定式定义：由to+动词原形构成。不定式是一种非限定性动词。而非限定动词是指那些在句中不能单独充当谓语的动词，可分为不定式，动名词，现在分词和过去分词。“动词不定式”由动词+不定式构成。动词不定式在句中可以作句子除谓语之外的任何句子成分。动词不定式的被动形式除了一般形式外还有其完成式和进行式。

时态、语态(介绍 (1)语态 (2)时态)

疑问词+不定式结构

语法功能(一、作主语 二、作宾语 三、作补语 四、作表语 五、作状语 介词 六、作定语)

省to的动词不定式(介绍 典型例题)

否定式not to do..

特殊句型

不定式与介词"to"区别

与动名词区别与联系

与动名词语义不同(目录 1 forget doing/to do 2 stop doing/to do 3 remember doing/to do 4 regret doing/to do 5 cease doing/to do 6 try doing/to do 7 go on doing/to do 8 be afraid doing/to do 9 be interested doing/to do 10 mean to doing/to do 11 begin(start) doing/to do)

被动式的用法(一、不定式被动式的用法 二、不定式完成被动式的用法)

完成式的用法(一、表示发生在谓语动作之前的动作 二、表示在某个给定的时间之前已完成的动作 三、表示过去未曾实现的想法和愿望)

在There be句型中用法

时态、语态

介绍

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：

(1)语态

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：These is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)

(2)时态

1) 现在时：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。

2) 完成时：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.

3) 进行时：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.

4) 完成进行时：

She is known to have been wreaking on the problem for many years.

一般在情绪后加to do to do 也表将来

疑问词+不定式结构

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：

①When to leave for London has not been decided yet. （不定式在句子中做主语）

②Mr. Smith didn't know whether to leave or stay there. （不定式在句子中做宾语）

③I asked Professor Xu how to learn English well. （不定式在句子中做直接宾语）

④The 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：①When 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,lea rn,observe,understand,wonder等。

语法功能

一、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：

(1)把不定式置于句首。如：

To get there by bike will take us half an hour.

(2)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：

①It+be+名词+to do

It's our duty to take good care of the old.

②It takes sb+some time+to do

How long did it take you to finish the work?

③It+be+形容词+for sb+to do

It is difficult for us to finish writing the composition in a quarter of an hour.

④It+be+形容词+of sb+to do

It is stupid of you to write down everything (that) the teacher says.

⑤It 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 helpme with my English.

(3)举例

（1） It's easy (for me) to do that.我做这事太容易了

easy,　difficult,　hard,　important,　possible,　impossible,　comfortable,　necessary,　better;

the first,　the next,　the last,　the best,　too much,　too little,　not enough

It's so nice to hear your voice.

听到你的声音真高兴。

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。

（2） It's very kind of him to help us.　他帮助我们，他真好。

Kind,　nice,　stupid,　rude,　clever,　foolish,　thoughtful,　thoughtless,　brave,　considerate(考虑周到的),　silly,　selfish(自私的)

例句:

It was silly of us to believe him.　我们真愚蠢，竟然相信了他。

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.　眼见为实。

(错)It is to believe to see.

二、作宾语

1) 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）

举例：

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+疑问词+ 不定式

decide,know,consider forget,learn,remember,show,understand,see,wonder,hear,find out,explain,tell

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 buy.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 foreignlanguage well.

He feels it his duty to help the poor.

I find it difficult to learn English well.

三、作补语

1) 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

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。

I found him lying on the ground.

I found it important to learn.

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

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 do sth. 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…

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

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。

四、作表语

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 of the 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。

④Our work is serving the people.

⑤What he likes is taking a walk after supper.

⑥The 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 our 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。

五、作状语

（1）目的状语

To… only to (仅仅为了),　in order to,　so as to,　so(such)… as to… (如此……以便……)

He ran so fast as to catch the first bus.　他飞快地跑以便赶上第一班车。

I 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。

What have I said to make you angry.

He 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。

六、作定语

⒈不定式作定语

不定式在句中作定语，置于被修饰的名词或代词之后。如：

①The next train to arrive is from Washington.

②Do you have anything to be taken to your sister?

③Do you have anything to say on the question?

④Would you please give me some paper to write on?

⑤My wish to visit France has come true at last.

不定式短语作定语和被修饰词之间表示以下关系：

(1)表示将来的动作（例①）。

(2)与被修饰词之间有动宾关系，如是不及物动词，则需加介词（例④）。

(3)与被修饰词之间有动宾关系，同时与句中其它词之间又有逻辑上的主谓关系时，尽管有被动含义，却仍 用主动语态（例③）；如只有动宾关系，而无逻辑上的主谓关系，则需用被动语态（例②）。

(4)不定式作定语时，一般可转换为定语从句，例①to arrive=that will arrive。

省to的动词不定式

介绍

（1） 情态动词( 除ought 外，ought to意思是“应该”，是情态动词，只有一种形式，后边接动词不定式，to不能省略。ought to没有人称和数的变化，后接动词原形可以表示现在、将来或过去将来，由时间状语或上下文决定。例如：

They ought to come tomorrow.他们明天应当来)：

（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。

在使役动词中get除外(get sb. to do sth.)

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） 表示个人意愿或倾向的would rather，had better，might(just) as well：rather than置于句首时。

Rather than ride on a crowded bus,he always prefers to ride a bike.

（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.

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。

否定式not to do..

Tell him not to shut the window…

She pretended not to see me when I passed by. 我走过的时候，她假装没看见。

典型例题

（1）Tell him ___ the window.

A. to shut not　B. not to shut　C. to not shut

D. not shut

答案：B。tell sb to do sth 的否定形式为tell sb not to do sth.

（2)　She pretended ___ me when I passed by.

A.　not to see　B. not seeing　C. to not see

D.　having not seen

答案：A。pretend 后应接不定式。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. 的否定形式为warn sb not to do sth. 此处用的是否定词never.

（4) The boy wanted to ride his bicycle in the street，but his mother told him ____.

A. not to　B. not to do　C. not do it

D. do not to

答案：A。not to 为not to do it 的省略形式。可以只用to这个词，而不必重复整个不定式词组。及物动词do后应有名词、代词等，否则不对，因此B，D不对。

（5) The patient was warned ___ oily food after the operation.

A. to eat no　B. eating not　C. not to eat

D. not eating

答案：C。warn一词要求后用不定式，此处为不定式的被动，否定形式为be warned not to do。

特殊句型

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。

（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。

不定式与介词"to"区别

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

介词but,except,besides+to do(do)

在这种句型中，如介词前有动词do，后面应接不带to的不定式；如无do，则接to不定式，即带do不带to， 带to不带do。如：

The enemy soldiers had no choice but to give in.

On Sunday afternoon I had nothing to do but watch TV.

与动名词区别与联系

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know,understand等状态动词连用时，如：I soon began to understand what was happening.

⒋advise,allow,encourage,forbid,permit等动词后接动名词作宾语，或带不定式作宾语补足语。如：

Our teachers don't permit our/us swimming in the lake.

Our teachers don't permit us to swim in the lake.

4 部分动词后接不定式或动名词时，意义差别较大，应根据句子语境选择使用。

①forget,remember,regret后接不定式，表示现在或未来的动作，接动名词表示动作已经发生。如：

Don't forget to post the letter for me.

Have you forgotten meeting her in Beijing Airport?

Remember to close the windows before you leave.

I remember writing him a letter a year ago.

We regret to tell you that all of you are not invited toattend the meeting.

They regretted ordering these books from abroad.

与动名词语义不同

目录

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，停了会聊天。

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.

⒉动词不定式的时态，语态

(1)时态

①一般式：动词不定式一般式表示的动作发生在谓语动词之后，有时表示同时发生.如：

I hope to become a university student this year.(to become发生在hope之后)

We often hear Dick play the piano in the next room.(play和hear同时发生)

②完成式：表示的动作发生在谓语动词所表示的动作之前.如：

I'm sorry to have kept you waiting.

We are too young to have seen the old society.

③进行式：表示的动作与谓语动词同时发生.如：

The teacher happened to be correcting our papers when I came in.

They seemed to be discussing something important.

(2)语态

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)

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：These is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)

⒊动名词的时态，语态

(1)时态

①一般式：动名词的一般式所表示的动作可以是泛指，也可与谓语动词同时发生，或发生在谓语动作之前或之后，如：

We are interested in collecting stamps.

I shall never forget seeing the Great Wall for the first time.

We are not afraid of dying.

②完成式所表示的动作发生在谓语动词之前，如：

Imagine having travelled on the moon.

We were praised for having finished the work ahead of time.

(2)被动语态

①如果动名词的逻辑主语为动名词所表示的动作的承受者，动名词要用被动语态，动名词的被动语态有一般式与完成式之分，如：

The young man came in without being noticed.

He prided himself on having never been beaten in class.

②有些动词后的动名词用主动形式，但表示被动意义，如：

The bike needs repairing.

If a thing is worth doing,it is worth doing well.

⒋在口语中，为避免重复，常用“to”代替不定式结构，有时甚至可以把to省略，如：

①-Did you go to visit the Great Wall

-No,I wanted to,but there wasn't enough time.

②-Would you like to come to a party

-I'd love to.

③-Don't make any mistakes in your homework,will you

-I'll try not to.

④-Try to be back by 12,won't you

-OK,I'll try.

另外，be going to,ought to,used to等也常用于这一结构中。

⒌在why引起的问句中，省略“to”，如：

Why spend such a lot of money

Why not wait for a couple of days

⒍当两个或更多作用相同的不定式并列使用时，只在第一个不定式前加“to”，如：

It's quite necessary for us to read more and have more practice.

⒎“to”在下列短语中是“介词”，后接动名词或名词形式，如：

devote…to,face up to(勇敢地面对),look forward to(盼望),object to(反对),take to(养成习惯，对……感兴趣；开始从事某种活动),be used to(习惯于)等。

被动式的用法

一、不定式被动式的用法

不定式到底用主动形式还是被动形式，往往取决于句子的意思，即意思上为主动就用主动形式，意思上为被动就用被动形式：

Did it need to be done so soon? 这事需要这么快就做吗?

She can’t bear to be laughed at. 她受不了被人嘲笑。

There was business to be taken care of. 有生意要人管理。

It remains to be seen whether you are right. 你是否正确，以后见分晓。

There was a lot of rubbish to be got rid of. 有大量垃圾需要扔掉。

二、不定式完成被动式的用法

不定式的完成被动式表示发生在谓语动作之前的被动动作：

I’m pleased to have been given this opportunity. 给了我这次机会我很高兴。

It’s said to have been built in the Ming dynasty. 据说它是明朝修建的。

完成式的用法

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. 我后悔和她吵架了。

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。

在There be句型中用法

在There be句型中的动词不定式：

For example one,There are too much homework to write.

two,There are students writing too much homework.