不定式to-do的作用

重点中学英语语法讲义-不定式一、概说动词不定式是非谓语动词的一种，它通常由不定式符号to +动词原形构成，但有时to也可省略(省略to的不定式叫不带to的不定式，与动词原形同形)。动词不定式具有名词、形容词、副词的功能，在句中可用作主语、表语、宾语、定语、状语、宾语补足语等，但不能用作谓语(故称不定式为非谓语动词)。不定式可以有不同的时态(如进行式、完成式等)和语态(主动语态和被动语态)。二、不定式的否定式1.不定式的否定式的构成通常是将否定词not或never置于不定式之前，即构成not to do或never to do的形式，注意not和never一定要放在不定式符号to的前面，而不是其后面。如：The doctor advised me not to smoke.医生劝我不要抽烟。Father warned me never to drive after drinking.父亲警告我不要酒后开车。注：若不定式为完成式和被动式，否定词应置于整个结构之前：She pretended not to have seen him.她假装没看见他。It is nice not to be dependent on others.不依靠别人是好的。2.so as to do sth和in order to do sth的否定式对于这两个结构的否定式，通常是将否定词置于不定式符号to之前，而不是置于整个结构之前或其他位置：Study hard so as not to fail the exam.努力学习，以免考试不及格。He came in quietly in order not to wake his wife.他轻轻进来，以免把他妻子吵醒。三、不定式的时态与语态1.不定式时态与语态的基本形式(以do为例)主动语态被动语态一般式to doto be done进行式to be doing无完成式to have doneto have been done完成进行式to have been doing无2.不定式一般式的用法有两个主要用法：(1)一是表示将来，即表示发生在谓语动作之后的动作：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：He seems to be tired.他似乎累了。Who heard him say that?是谁听到他这样说的？Im sorry to hear that.听到这事我很难过。(to hear略先于am sorry)2.不定式进行式的用法主要用法有：(1)表示与谓语动作同时发生且正在进行的动作：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。(2)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：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。3.不定式完成式的用法(1)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。Im sorry to have given you so much trouble.对不起给了你这么多麻烦。(2)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。(3)表示过去未实实现的想法和愿望：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。4.不定式完成进行式的用法表示在谓语动作之前一直在进行的动作：You seem to have been writing very long.你好像已经写了很久了。The battle was said to have been going on for two days.据说战斗已经进行两天了。5.不定式被动语态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?It remains to be seen whether you are right.你是否正确，以后见分晓。Im pleased to have been given this opportunity.给了我这次机会我很高兴。注：有关不定式用主动形式表示被动意义的内容，参见本讲义“被动语态”之内容。句子中的作用:1. 作主语To see is to believe. 眼见为实。To talk with him is a great pleasure. 和他谈话是一件非常愉快的事。To remember this is very important. 记住这一点很重要。注：为了避免头重脚轻，在许多情况下，通常都将作主语的不定式置于句子后部，而在句首使用的主语位置使用形式主语it：Its very important to remember this. 记住这一点很重要。Its a pity to leave so early. 这么早走太遗憾。2.作表语He seems to be ill. 他似乎有病。Her wish is to be a teacher. 她的愿望就是当一名教师。You are not to smoke in this room. 你不应在这个房间里吸烟。注：不定式作表语主要有三种情况，一是用于seem, appear, prove, turn out等连系动词之后的不定式(尤其是to be)，二是像My job is to sweep the floor(我的工作就是擦地板)这样的主语与表语“等价”的情形，三是表示想法、约定、义务、命令、可能性、命运等，再如：We are to meet at the station at three. 我约定3点钟在车站见面。(表约定)How are we to convince him? 我们怎么能说服他呢? (表可能性)You are to come when I call. 叫你来的时候，你必须来。(表命令)3. 作宾语I cant afford to buy a car. 我买不起汽车。Remember to post the letter. 记住把信寄了。I hope to be staying with you. 我希望和你住在一起。注：不定式不仅用作动词的宾语，还可用作个别介词(如but, except)的宾语：I had no choice but to wait. 除了等，我没有别的选择。It had no effect except to make him angry. 除惹他生气外，没产生任何效果。4. 作宾语补足语Who taught you to drive? 谁教你开车的? He warned me not to touch it. 他警告我不要触碰它。What caused him to change his mind? 什么使他改变主意的? 注：当作宾语的不定式后跟有宾语补足语时，通常要用形式宾语it代替不定式，并将真正的宾语不定式置于宾语补足语之后：It find it difficult to learn Japanese well. 我感到学会日语不容易。5. 作定语I have a question to ask you. 我有一个问题要问你。It is a pleasant thing to remember. 这是一件值得记住的愉快的事。He is not a man to tell a lie. 他不是个说谎的人注：有的名词(如way, chance, right等)后用作定语的不定式可换成of doing sth：Its the best way to do of doing it. 这是做此事最好的办法。但是，以下名词后接不定式作定语时通常不能换成of doing sth：attempt 试图 courage 勇气 decision 决定 effort 努力 fortune 运气failure 失败 invitation 邀请 permission 允许 promise 允诺 wish 愿望6. 作状语不定式作状语可以表示多种关系(如目的、结果、原因、条件等)：I went to France to learn French. 我到法国去学法语。(表目的)He returned home to find his wife waiting for him. 他回到家发现他的妻子在等他。(表结果)You would make a great mistake to accept his offer. 你要是接受他的建议，你就犯了大错误。(表条件)We are proud to be members of this team. 作为这个队的队员我们感到很自豪。(表原因)He opened his mouth as if to say something. 他张开嘴，好像要说什么。(表方式)五、通常要接不定式作宾语的动词通常只接不定式(而不是动名词)作宾语的动词有：afford负担得起agree同意 arrange安排，设法ask要求care想要 choose决定 decide决定 demand要求determine决心 expect期待fail未能 help帮助hesitate犹豫 hope希望 long渴望 manage设法offer主动提出 plan计划 prepare准备pretend假装promise答应 refuse拒绝want想要wish希望I cant afford to buy a car.我买不起汽车。She refused to help me.她不肯帮助我()。He agreed to come over right away.他同意马上就来。He managed to avoid an accident.他设法避免了一次事故。The boy decided not to become a sailor.那孩子决定将来不当水手。He chose not to go abroad until later.他决定晚点出国。He pretended not to know the facts.他佯装不知实情。六、“动词+宾语+不定式”用法说明1.可用于该结构的常用动词通常可带不定式作宾语补足语的动词：advise, allow, ask, bear, beg, cause, command, encourage, expect, forbid, force, get, hate, help, intend, invite, leave, like, mean, need, oblige, order, permit, persuade, prefer, request, remind, teach, tell, trouble, want, warn, wish等。如：He didnt allow the students to go there.他没让学生们去那儿。He ordered the work to be started at once.他命令马上开始工作。He forbade me to use his car.他不准我用他的小车。The doctor warned him not to smoke.医生告诫他不要抽烟。My parents encouraged me to study abroad.父母鼓励我出国留学。I tried to persuade him to leave, but he wouldnt listen.我想劝他离开，可他不听。2.容易误用于该结构的动词容易受汉语意思误用不定式作宾语补足语的动词：汉语可说“害怕某人做某事”，但英语不说fear sb to do sth。汉语可说“原谅某人做某事”，但英语不说excuse forgive sb to do sth。汉语可说“拒绝某人做某事”，但英语不说refuse sb to do sth。汉语可说“惩罚某人做某事”，但英语不说punish sb to do sth。汉语可说“建议某人做某事”，但英语不说suggest propose sb to do sth。汉语可说“赞成某人做某事”，但英语不说approve sb to do sth。汉语可说“通知某人做某事”，但英语不说inform sb to do sth。汉语可说“欢迎某人做某事”，但英语不说welcome sb to do sth。汉语可说“坚持某人做某事”，但英语不说insist persist sb to do sth。汉语可说“希望某人做某事”，但英语不说hope sb to do sth。汉语可说“安排某人做某事”，但英语不说arrange sb to do sth。汉语可说“要求某人做某事”，但英语不说demand sb to do sth。汉语可说“感谢某人做某事”，但英语不说thank sb to do sth。汉语可说“祝贺某人做某事”，但英语不说congratulate sb to do sth。汉语可说“阻止某人做某事”，但英语不说prevent sb to do sth。要表示以上意思，可换用其他表达：汉语的“原谅某人做某事”，英语可说成excuse forgive sb for doing sth。汉语的“希望某人做某事”，英语可说成wish sb to do sth。汉语的“建议某人做某事”，英语可说成advise sb to do sth。汉语的“安排某人做某事”，英语可说成arrange for sb to do sth。汉语的“要求某人做某事”，英语可说成demand of sb to do sth。汉语的“感谢某人做某事”，英语可说成thank sb for doing sth。汉语的“祝贺某人做某事”，英语可说成congratulate sb on doing sth。汉语的“阻止某人做某事”，英语可说成prevent sb from doing sth。3.关于promise sb to do sth该结构中的不定式的逻辑主语不其前的宾语sb，而是句子主语，所以严格说来，此句中的不定式不是宾语补足语，如He promised me to go.的意思是“他答应我他去”，而不是“他答应让我去”。七、省略to的若干情况1.使役动词后省to的情况在let, make, have等使役动词后用作宾语补足语的不定式必须省略to：My mother wouldnt let me go to the film.我妈妈不会让我去看电影的。I dont like milk, but she made me drink it.我不喜欢牛奶,可是她强迫我喝。I would have him wait for me at the gate of the park.我要他在公园门口等我。注：(1)当使役动词用于被动语态时，要补上在主动语态中省略的to(主要是指make，let和have很少用于被动语态)。(2)force, oblige等虽然也表示“使”，但它们后用作宾语补足语的不定式必须带to：He forced me to go with them.他迫使我同他们一起去。2.感觉动词后省to的情况在感觉动词后用作宾语补足语的不定式必须省略to：I saw the woman enter a bank.我看见这个女人进了一家银行。We often hear her sing this song.我们经常听到她唱这乎歌。Did you notice her leave the house?她离开屋子你注意到了吗? zI watched her get into the car.我看着她上了车。注：(1)这里所说的感觉动词主要包括see, hear, observe, notice, feel, watch。但是它们用于被动语态时，则其后的不定式必须带to：The woman was seen to enter a bank.有人看见这个女人进了一家银行。但是，用于以上句型的动词notice和watch通常不用于被动语态。(2)类似地，动词look at和listen to后用作宾语补足语的不定式也不带to：We listened to the old man tell his story.我们听这位老人讲述他的经历。(3)若动词feel后用作宾语补足语的不定式为to be，则要带to(其他情况不带to)：They felt the plan to be unwise.他们认为这个计划不明智。(4)若不定式为完成式，通常应带to。如()：I noticed her to have come early.我注意到她来得很早。2.动词help后省to的情况在动词help后用作宾语或宾语补足语的不定式可以不带to：Can I help (to) carry this heavy box?我可以帮忙扛这个重箱子吗？Mother helped me (to) do my homework.妈帮助我做作业。注：(1)当help之后接一个较长的名词词组作宾语或当其中的不定式所表示的动作主语不直接参加时，不定式通常带to：Help the little boys at the back ofthe hall to carry the chairs out.请帮大厅后面那些小男孩把椅子搬出去。These tablets will help you to sleep.这些药片将对你的睡眠有帮助。(2)在当help用于被动语态时，不定式前的to不能省略：The boy was helped by a woman to collect his scattered coins.那男孩由一个妇女帮他捡拾散乱一地的钱币。4.why (not)后省to的情况在why (not)?之后的不定式不能带to：Why go with him?为什么要同他一起去？Why not ask the teacher?为什么不去问问老师？5.动词know后省to的情况在“know+宾语+不定式”中，不定式有时省to，有时不省，可分以下两种情况讨论：(1)若know为现在式，该结构中的不定式只限于to be，且其中的to不能省略：I know him to be ill.我知道他病了。(2)若know为完成式或过去式，则该结构中的不定式可以用除to be外的其他动词，且此时其中的to可以省留：I never knew him (to) do such a thing.我从未听说他会干那种事。Weve never known him (to) tell a lie.我们从未听说他撒过谎。但在被动语态中不定式前的to不能省略。这样用的know不仅仅表示一般意义的“知道”，而是表示一种经历，因此常译为“曾过”(用于肯定句时)或“(从来)没有过”(用于否定句时)。6.介词except和but后省to的情况用作介词except, but宾语的不定式有时带to，有时不带to。其大致原则是：若其前出现了动词do，其后的不定式通常不带to；若其前没有出现动词do，则其后的不定式通常带to：I had no choice but to wait.除了等，我没有别的选择。He wanted nothing but to stay there.他只想留在那儿。It had no effect except to make him angry.除惹他生气外，没产生任何效果。She can do everything except cook.除了做饭之外她什么都会。7.主语带do表语省to的情况当主语部分有动词do的某种形式时，用作表语的不定式可以省略to：All you do now is (to) complete the form.你现在要做的只是把这张表填好。The only thing to do now is (to) go on.前进是现在惟一的出路。What Ill do is (to) tell her the truth.我要做的就是告诉他真相。8.并列不定式省to的情况当两个或多个作用相同的不定式并列时，通常只需在第一个不定式前用to，其余不定式前的to可以省略：He told me to stay there and wait him.他叫我在那儿等他。Im really puzzled what to think or say.我真不知该怎么想怎么说。It is easier to persuade people than (to) force them.说服人容易，强迫人难。但是，如果两者有对比关系，则后面不定式前的to不可省略：To try and fail is better than not to try at all.尝试而失败总比不尝试好。9.省略不定式是否保留to在一定的上下文中，为了避免重复，有时不定式可以省略，但通常保留不定式符号to：I shall go if I want to.如果我想去就去。Dont be late. Ill try not to. “不要来晚了。”“我尽量不来晚。”Dont go till I tell you to.等我叫你走你再走。注：(1)若被省略的不定式为to be短语，则通常应保留be：He is not the man he used to be.他已不是原来的那个样子了。(2)有时省略不定式时，同时也可省略to：She may go if she likes (to).他想去就可以去。八、“wh-词+不定式”结构1.该结构的句法功能“wh-词+不定式”主要用作宾语：We must think what to do.我们必须考虑怎么办。I cant decide whom to invite.我不能决定该邀请谁。He had no idea of how to do it.他不知道如何做此事。除用作宾语外，还可用作主语、表语等：When to leave has not been decided.何时离开还没有决定。The question is how to find him.问题是如何找到他。2.该结构与why原则上说，why后不接不定式，不过若不定式不带to，则可用why：Why not go there at once?为什么不马上去那儿呢?Why argue with her?为什么要跟她争论呢?注：这类结构通常只用于谈论现在和将来，不用于谈论过去：误：Why not clean the room yesterday?正：Why didnt you clean the room yesterday?你昨天为什么不打扫房间?3.该结构与how有些动词后接“how+不定式”作宾语时，how可省略：Did you learn (how) to drive a car?你学过开车吗？但是，有些动词后面接“疑问词how+不定式”作宾语时，尽管其中的how在汉语中无需译出，但却不能将how省略：He knows how to play the piano.他会弹钢琴。He showed her how to swim.他教她游泳。Soon youll find out how to drive a car.不久你就会学会开车的。We never discovered how to open the box.我们一直未发现如何打开这个盒子。Can you explain how to make a cake?你可以给我解释一下怎么做蛋糕吗？九、重点考点原创精练1._ the seeds and they will grow.A. WaterB. To waterC. WateringD. Watered2.The purpose of the scheme is not to help the employers but _ work for young people.A. provideB. to provideC. providingD. provided3.He arrived at the office early, _ a good example to the others.A. setB. to setC. to be setD. having set4.Please make my excuse at tomorrows meeting Ive got too much work _.A. to do to comeB. doing comingC. to do comingD. to do coming5.We looked everywhere for the keys, but they are nowhere _.A. to findB. to have foundC. to be foundD. being found6.After describing the planned improvements, she went on _ how much they would cost.A. to explainB. explainingC. to be explainingD. having explained7.To test eggs, _ them in a bowl of water: if they float theyre bad, if they sink theyre good.A. putB. puttingC. to putD. to be putting8.Please remember _ the plants while Im away.A. wateringB. to be wateringC. to waterD. being watering9._ wine, first you must press the grapes.()A. MakingB. To makeC. To be makingD. Make10.Ive never been so poor _ able to afford a meal.A. as to be notB. not as to beC. as not to beD. as to not be11.I dont know whether to stay in teaching or _ another job.A. trying gettingB. to try to getC. trying to getD. try get12.Ill have to change my clothes before I go out I dont want _ like this.A. to seeB. to be seeingC. to be seenD. being seen13.In fact, she was the first woman _to such a post.A. to electB. to be electingC. to have electedD. to have been elected14.Id like _ over theAlpsand looking down at the mountains.A. flyingB. being flyingC. to be flyingD. be flying15.Im learning _ a cake. Can you explain _ one?A. to make, to makeB. how to make, to makeC. to learn, how to makeD. making, making16.Whom would you rather _ with you, Jim or Jack?A. have goB. have to goC. have goneD. has to go17.The husband advised _ to the south, but his wife advised him _ up the idea.A. moving, givingB. to move, to giveC. moving, to giveD. to move, giving18.“Would you like to come for a walk with me?” “Id prefer _, thank you.”A. not toB. to notC. notD. cant19.I would mend your radio, but I dont know _.A. howB. toC. how toD. to how20.“I havent heard from Henry for a long time.” “What do you suppose _ to him?”A. was happeningB. to happenC. has happenedD. had happened21.When I handed the report to John, he said that George was the person _.A. to sendB. for sending itC. to send it toD. for sending it to22.“Do you know the girl in red?” “She seems _ me at last months party. But Im not sure.A. to introduce to B. to be introduced toC. being introduced toD. to have been introduced to23.We all agreed _ for another day, but Jim disagreed _.A. to wait, to do soB. to wait,不填C. waiting, doing soD. waiting,不填24.He made up his mind to devote his life _ pollution _ happily.A. to prevent, to liveB. to prevent, from livingC. to preventing, to liveD. to preventing, from living25.I wish Id been there I would like _ her face when his husband came in.A. to seeB. to have seenC. seeingD. having seen参考答案：0105 ABBAC0610 AACBC1115 BCDCC1620 ACACC2125 CDBCB动词不定式作主语时常用it作形式主语，而往往将动词不定式放在谓语或表语之后。如：Its not easy to learn a foreign language well. (=To learn a foreign language well is not easy.) 学好一门外语不容易。 在此句型中，如果要说明动词不定式的动作是谁做的，可在不定式前加一个for 引起的短语，作不定式的逻辑主语。如：Its difficult for us to finish the work. 对我们来说，完成这项工作很困难。Its hard for me to answer your question. 要我回答你的问题很难。但是，如果表语是kind, nice, right, wrong, clever, polite 等描述行为者的性格、品质的形容词，则应在不定式前加一个of 引起的短语。如：这个例子属于上面的换一个of引起的。Its very kind of you to help me.你能帮我，真好。注意：1. of sb.和for sb.这两种结构还有一个区别，在of sb.结构中，可用sb.直接作句子的主语来改写成“Its形容词of sb.动词不定式”结构。试比较：Its foolish of him to go alone. (=He was foolish to go alone.) 他单独出去太傻了。Its kind of you to give me the book. (=You are kind to give me the book.) 你给我这本书，真是太好了。for sb.结构则不能这样转换。例如，不可以说：We are difficult to finish the work. 2. 动词不定式作主语，同时有另一个不定式作表语时，不能转换成“Its.to do sth.”的句型。如：正 To see is to believe. 百闻不如一见。误 Its to believe to see.二、“疑问代(副)词+动词不定式”也可以在句中作主语。如：How to control the water pollution is a big problem. 如何控制水污染是一个大问题。When to start the project remains undecided. 什么时候开始这项工程仍然没有决定。一、不定式等非谓语形式作主语时，谓语动词一路走来都是单数身份；不少作主语的不定式与动名词在意义上相同。如： To see is to believe. = Seeing is believing. 眼见为实。 二、口语中，当作主语的不定式过长时，it不惜屈居有名无实的形式主语，常为平衡关系而挺身而出、替主出征，真主角反无官一身轻，悠哉断后。如： To learn a foreign language well is not easy. Its not easy to learn a foreign language well. 要把一门外语学好不容易。 To play football is very interesting. Its very interesting to play football. 踢足球很有趣。 留言提醒：在实际操作中，不定式（短语）还有权招聘一个逻辑主语，并由of / for出面料理-Its + adj. + for / of sb. + to do sth.，下例中的for me即是： Its hard for me to finish the task in such a short time. 对我而言，要在如此短的时间里完成任务是困难的。 聘of还是for？点击作表语的形容词属性可知：若形容词描述的是人的特征与品行，能修饰人（像kind， nice， good， clever， right， polite， careless等），则of适宜；如果形容的是事物的特点或外观等（如easy，hard / difficult， safe， interesting， important，necessary之类），则for主动上！下例正误可略见一斑： 不定式可用作哪些状语本站特约作者 龙楠从句法上看，不定式在句子中可以用作主语、宾语、定语、状语、补语等，其中用作状语是不定式所有用法中最重要的用法之一，同时也是英语考试的重要考点。本文专门为大家归纳不定式作状语的用法，帮助大家理清思路，搞清用法。先提醒一下，在不定式用作状语的所有用法中，用作目的状语是最重要的（几乎每年都有所考查），其次是用作结果状语（尤其要注意only to do sth这类表示意外结果的用法），用作条件状语也要适当引起注意，而用作方式状语和原因状语则相对考得较少。一、用作目的状语不定式用作目的状语属不定式的常见用法，也是英语考试的一个高频考点。如：_, you need to give all you have and try your best.A.Being a winnerB.To be a winnerC.Be a winnerD.Having been a winner此题答案为B。不定式用于句首表示目的（即用作目的状语）。句意为：要想获胜，你必面要倾其所有，全力以赴。不定式用作目的状语有两个可能的位置，一是在句首，二是在句末。