不定式定义由to+动词原形构成

1、1. 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。2.用途：在句中不能作谓语。它具有动词的性质，本身可以带宾语和状语。【动词不定式】1.定义：动词 + 不定式2.用途：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。动词不定式的时态、语态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

2、。这一使动者我们称之为 逻辑主语，其形式如下：主动形式 被动形式一般式 （not) to done（not) to be done 完成式 （not) to have made ( not) to have been done进行式 （not) to be doing无被动完成时（not）to have been done无被动(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

3、 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

4、 (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

5、。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

6、,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. （不定式在句子中做间接宾语）The question was where to get the medicine needed. （不定式

7、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 leavehow 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。动词不定式的语法功能一、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

8、. (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： Itbe名词to do It's our duty to take good care of the old. It takes sb+some time+to do How long did it take you to finish the work? Itbe形容词for sbto do It is difficult for us to finish writing the compositionin a quarter of an hour. Itbe形容词of sbto do It is stu

9、pid of you to write down everything the teachersays. It seems(appears)形容词to do It seemed impossible to save money. 在句型中，常用表示客观情况的形容词，如：difficult,easy,hard,important,impossible,necessary 等；在句型中，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

10、一句式有时相当于Sb is形容词to do句式 ，如：It'skind 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

11、,not enoughIt'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 w

12、as 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.百闻不如一见。(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）

13、，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

14、），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） pretend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

15、定式decide, know, consider forget, learn, remember, show, understand, see, wonder, hear, find out, explain, tellPlease 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 q

16、uestion 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)adviseallow

17、appointbelievecausechallengecommandcompelconsiderdeclaredriveenableencouragefindforbidforceguesshireimagineimpelinduceinforminstructinvitejudgeknowlikeorderpermitpersuaderemindreportrequestrequireselectsendstatesupposetellthinktraintrustunderstandurgewarn例句：a.Father will not allow us to play on the

18、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，dea

19、d.A. lyingB. lieC. layD. 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),feelfind,guess,judge,imagine,know,prove,see(理解), show,suppose,take(以为),understand We consider Tom to be one of the bes

20、t 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 inventB. inventingC. to have inventedD. 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,b

21、e supposed,be believed,be thought,be known,be reported,hope, wish,desire,want,plan,expect,meanThe 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, undrstandWe didn't expect there to be so many people there.我们没料到会有那么多人在

22、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。 To be kind to the enemy is to be cruel to the people. My chief purpose is to point out the difficulties ofthe mat

23、ter. What 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）。当主语是aim,duty,hope,idea,mista ke,plan,purpose,suggestion等为中心词的名词词组（例）时，或以what引导的名词性分句（例），不定 式说明主语的内容。 Our work is serving the people. What he likes is taking a walk after supper. The story told by Mr.Wang is interesting

24、. 句动名词作表语，与主语部分可以转换，如Serving thepeople is our work,而句中是现在分词作 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

25、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. sitB. sit onC. be seatD. 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、

26、作定语不定式作定语 不定式在句中作定语，置于被修饰的名词或代词之后。如： The next train to arrive is from Washington. Do you have anything to be taken to your sister? Do you have anything to say on the question? Would you please give me some paper to write on? My 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

27、将来的动作（例）。 (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）。 (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）；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）。 (4)不定式作定语时，一般可转换为定语从句，例to arrive=that will arrive。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, l

28、isten 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。 使役动词中get除外(get sb. to 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

29、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

30、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,no

31、t 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 goingB.trying to goC.to try and goD.try going答案：D. why not 后面接不带to 的不定式，因此选D。2） Paul

32、doesn't have to be made _. He always works hard.A. learnB. to learnC. learnedD. 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。动词不定式的否定式Tell him not to shut the windowShe 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 notB. not to shutC. to not s

33、hutD. 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 seeB. not seeingC. to not seeD.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 driveB. to never driverC. nev

34、er drivingD. 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 toB. not to doC. not do itD. 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

35、) The patient was warned _ oily food after the operation.A. to eat noB. eating notC. not to eatD. 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。 不定式的特殊句型1、不定式的特殊句型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。

36、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 t