不定式在句子中可做主語、賓語、表語、定語、狀語和賓語補(bǔ)語.
1)不定式做主語一般表示具體的某次動(dòng)作.
【例如】
To complete the 30?storied building in one year was quite a difficult task.
To do that implies taking responsibility.
當(dāng)主語較長(zhǎng),謂語較短時(shí),常用it做形式主語,而將不定式放到謂語的后面.
【例如】
It is important for modern young people to master at least two foreign languages.
It做形式主語,不定式放在謂語動(dòng)詞之后常用于下列結(jié)構(gòu)中：
a) It is＋形容詞(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＋名詞(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)不定式作表語不定式作表語常表示將來的動(dòng)作,主語常常是表示意向、打算、計(jì)劃的詞,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)不定式作賓語不定式常在下列動(dòng)詞后面作賓語：
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.根據(jù)句意,他看起來非常生氣,他想找麻煩,不定式的動(dòng)作還沒有實(shí)施,應(yīng)用一般式,因此答案為B.不定式作賓語還常用在下面結(jié)構(gòu)中；主語＋動(dòng)詞＋it＋形容詞＋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.
使用這種句型的常見動(dòng)詞有：believe, consider, declare, feel, find, guess, imagine, prove, realize, suppose, think,等.
4)“wh?word＋不定式”結(jié)構(gòu)不定式前加一個(gè)疑問代詞(what, which, who, whom, whose)或疑問副詞(where, when, how, why),以及連詞whether構(gòu)成特殊的不定式短語,其作用相當(dāng)于一個(gè)從句,這樣的不定式短語常在某些動(dòng)詞后面作賓語.
常見的可以接這種不定式短語的動(dòng)詞有：
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”結(jié)構(gòu)除了作賓語外,還可以在句中作主語或者表語.
【例如】
When to start the program remains undecided. The question is how to put the plansintospractice.
5)不定式作狀語
a)不定式作狀語表示目的.或用于so as和in order之后,來強(qiáng)調(diào)這種目的.
【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)不定式表示結(jié)果,特別是在so...as to, such...as to, only to...以及too...to等結(jié)構(gòu)中的不定式表示結(jié)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)不定式常用來修飾形容詞,構(gòu)成下列詞組：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)不定式作賓語補(bǔ)語不定式常跟在下列動(dòng)詞之后作賓語補(bǔ)語：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.
當(dāng)不定式在let, make, have, hear, look at, listen to, feel, observe, watch, notice, perceive(感覺到)等動(dòng)詞后面作賓語補(bǔ)語時(shí),不定式不帶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)不定式作主補(bǔ)帶有賓語及賓語補(bǔ)足語結(jié)構(gòu)的動(dòng)詞變?yōu)楸粍?dòng)語態(tài)時(shí),原來的賓語變?yōu)橹髡Z,賓補(bǔ)則變?yōu)橹餮a(bǔ).加主補(bǔ)的動(dòng)詞主要有：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)不定式作定語
a)不定式作定語通常要放在其所修飾的名詞或代詞之后.
不定式常作下列的名詞定語：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后面應(yīng)接后置定語,表示競(jìng)爭(zhēng)的壓力.單個(gè)分詞作定語一般置于名詞前,故B和D可以排除.C為不定式的被動(dòng)式,而競(jìng)爭(zhēng)和壓力之間沒有被動(dòng)關(guān)系,因此正確答案為A.特別注意的是在不定式與其修飾的名詞有動(dòng)賓關(guān)系時(shí),要根據(jù)句子的需要在不定式后加適當(dāng)?shù)慕樵~,這個(gè)介詞的選用取決于被修飾的名詞或不
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,序數(shù)詞或形容詞最高級(jí)修飾的名詞常用不定式作定語.
【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)不帶to的不定式在下列詞組后面的不定式不帶to：would rather ...than(寧愿……也不), had better...(最好),can't help but...(不得不), had
rather...(寧愿),cannot but...(不得不,必然),may/might as well...(不妨),let alone(更不用說).
【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.