一,作主語
⒈不定式作主語
動詞不定式作主語時,句子的謂語動詞常用單數,其位置有以下兩種:
(1)把不定式置於句首.如:
to get there by bike will take us half an hour.
(2)用it作形式主語,把真正的主語不定式置於句後,常用於下列句式中.如:
①it+be+名詞+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+形容詞+for sb +to do
it is difficult for us to finish writing the composition in a quarter of an hour.
④it+be+形容詞+of sb +to do
it is stupid of you to write down everything the teacher says.
⑤it seems(appears)+形容詞+to do
it seemed impossible to save money.
在句型③中,常用表示客觀情況的形容詞,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 表示讚揚或批評的詞.在不定式前的sb,可看作其邏輯主語.這一句式有時相當於sb is+形容詞+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.
⒉動名詞作主語
learning without practice is no good.
動名詞作主語時,也常用it句式.如:
①it's +no good(no use, fun, a pleasure, a waste of time)+doing…
it's no good reading in dim light.
it's no use sitting here waiting.
②it's+形容詞+doing
it's dangerous swimming in the sea in windy days.
這樣用的形容詞有expensive, nice, tiring等,但important, necessary則不適用於這種結構,套用不定式 代替,如:it's important for you to keep fit.
③there is no + doing
there is no saying what will happen next.
在這一結構中,動名詞後常帶賓語,相當於"it's impossible to…"結構.
⒊動詞不定式和動名詞作主語的區別
①不定式作主語經常表示具體動作,常與特定的動作執行者聯繫在一起;而動名詞作主語經常表示抽象動 作,經常不與特定的動作執行者聯繫在一起.如:
it's no good eating too much fat.
it's no good for you to eat so much fat.
②動名詞結構作主語,可以用名詞或代詞屬格形式作邏輯主語.如:
it's no use your pretending that you didn't know the rules.
二,作賓語
⒈不定式作賓語
①以下動詞後,只能跟不定式作賓語.如:agree, ask, aim, arrange, choose, decide, demand, expect, fail , help, hope, lean, long, manage, offer, plan, prepare, pretend, promise, refuse, wish等,這些詞大部分可接that引導的從句.如:
i decided to ask for my money back.
i decided that i would ask for my money back.
when our visit to the farm was over, we expected to start back on foot.
when our visit to the farm was over, we expected that we would start back on foot.
②當複合賓語中的賓語是不定式時,先用形式賓語it代替不定式,把不定式置於補語之後,即:主語+動 詞+it+補語+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.
③介詞but, except, besides +to do(do)
在這種句型中,如介詞前有動詞do,後面應接不帶to的不定式;如無do,則接to不定式,即帶do不帶to, 帶to不帶do.如:
the enemy soldiers had no choice but to give in.
on sunday afternoon i had nothing to do but watch tv.
⒉動名詞作賓語
①以下動詞後,只能接動名詞作賓語,如:admit, appreciate, consider, delay, enjoy, finish, keep, imagine, mind, miss, practise, resist, risk, save, suggest, don't mind, give up, insist, on, put off等.如:
i suggest spending our summer vacation in a seaside town.
you must give up smoking, for it does too much harm to your health.
②動名詞作介詞的賓語
i should go to attend the birthday celebration instead of staying at home.
what about inviting li jun to make a speech
動名詞前的介詞有時可以省略,如:have difficulty(in)doing, have no trouble(in)doing, lose no ti me(in)doing, prevent/stop…(from)doing, there is no use(in)doing等.
⒊部分動詞後面,既可接動詞不定式,也可接動名詞作賓語,意義不變.如:begin, continue, start, hat e, like, love, need, require, want等.
在need, require, want後接-ing形式,表示被動意義,也可接不定式,但要用被動形式,如:your handwriting needs improving (to be improved). hate, love, like接不定式表示特定的未來事件,接動名詞表示目前 正在進行的活動或一般的行為.
在下列情況下,一般要用不定式:
①hate, like, love前有would(should)時,如:i'd like to have a cup of coffee.
②當謂語動詞begin, continue, start等是進行式時,如:the students are starting to work on the difficult maths problem.
③begin, continue, start與know, understand等狀態動詞連用時,如:i soon began to understand what
was happening.
⒋advise, allow, encourage, forbid, permit等動詞後接動名詞作賓語,或帶不定式作賓語補足語.如:
our teachers don't permit our swimming in the lake.
our teachers don't permit us to swim in the lake.
⒌部分動詞後接不定式或動名詞時,意義差別較大,應根據句子語境選擇使用.
①forget, remember, regret後接不定式,表示現在或未來的動作,接動名詞表示動作已經發生.如:
don't forget fo 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 to attend the meeting.
they regretted ordering these books from abroad.
②mean to do 打算做某事
doing 意味著……
i meant to catch up with the early bus.
this means wasting a lot of money.
③try to do 設法盡力做某事
doing 試著做某事
you should try to overcome your shortcomings.
try working out the physics problem in another way.
④stop to do 停下一件事去做另一件事(不定式作目的狀語)
doing 停止做某事
on the way to the airport, i stopped to buy a paper.
you'd better stop arguing and do as you are told.
⑤can't help doing 禁不住……
to do不能幫助乾……
they couldn't help jumping up at the news.
sorry i have lots of work to do. so i can't help to make up the room for you.
⑥go on to do 做不同的事或不同內容的事
doing 繼續不停地做某事,指同一動作的繼續
he went on to talk about world situation.他接著又談了世界形勢.
we'll go on fighting so long as there is oppression in the world.
⑦leave off to do 離開某地去乾什麼(目的狀語)
doing停下某事
it's time to leave off talking and to start acting.
they left off to go fishing.
三,做表語
不定式作表語表示具體動作或將來動作;動名詞作表語表示抽象的一般行為.
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.
當主語和表語都是不定式時,其含義一是條件,一是結果(例①).當主語是aim, duty, hope, idea, mistake, plan, purpose, suggestion等為中心詞的名詞詞組(例②)時,或以what引導的名詞性分句(例③),不定 式說明主語的內容.
④our work is serving the people.
⑤what he likes is taking a walk after supper.
⑥the story told by mr. wang is interesting.
④⑤句動名詞作表語,與主語部分可以轉換,如serving the people is out work, 而⑥句中是現在分詞作 表語,說明主語的性質,狀態,現在分詞具有形容詞的各種特徵,另外,動名詞作表語還應與進行時態區別開 來.
四,作定語
⒈不定式作定語
不定式在句中作定語,置於被修飾的名詞或代詞之後.如:
①the next train to arrive is from washington.
②have you 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.
不定式短語作定語和被修飾詞之間表示以下關係:
(1)表示將來的動作(例①).
(2)與被修飾詞之間有動賓關係,如是不及物動詞,則需加介詞(例④).
(3)與被修飾詞之間有動賓關係,同時與句中其它詞之間又有邏輯上的主謂關係時,儘管有被動含義,卻仍 用主動語態(例③);如只有動賓關係,而無邏輯上的主謂關係,則需用被動語態(例②).
(4)不定式作定語時,一般可轉換為定語從句,例①to arrive=that will arrive.
⒉動名詞作定語
①this passage can be used as listening materials.
②the reading room of our school library can hold 800people.
③all moving bodies have energy.
①②句動名詞作定語說明一種性能,即:用來……的;第③句為現在分詞作定語,單個分詞作定語常置於 被修飾詞之前,與被修飾詞之間,可構成邏輯上的主謂關係,分詞短語作定語常置於被修飾詞之後.如:the man standing at the school gate is professor hua.
五,不定式作補足語
⒈作賓語補足語
一些及物動詞除要求按賓語外,有時還需要有賓語補足語,說明賓語的行為,狀態,特徵,這時意思才相 對完整.
(1)常要求不定式作賓補的動詞有:allow, ask, advise, beg, cause, drive(強迫),encourage, expect, forbid, force, get, would like(love, hate), order, permit, persuade, teach, tell, want, warn, wish等.如:
①would you like me to give your regards to mary
②i want you to understand the whole passage clearly.
(2)部分動詞後常接to be+形容詞,名詞短語等形式,有時to be可省略,如:believe, consider, discover, find(=consider), feel(=think), imagine, judge, know, prove, think, suppose, see(=understand), understand等.
①we all believe john(to be)honest.
②i consider him(to be)one of the best biology teachers of no. 1 middle school.
但當不定式是完成式時,to不能省略,如:we consider him to have been foolish.
(3)感覺動詞和使役動詞後用作賓補的不定式須省略to.
①i didn't hear anyone say anything about it.
②they make the students do too much homework every day.
這種句式在變為被動語態時,to不能省略,如第②句:the students are made to do too much homework every day.
(4)help, know後面的"to"可有可無.如:
would you please help me(to) fill in the tax form
i've never known her(to)be late before.但:he was known to have been to france before.
(5)部分短語動詞後,常接不定式作賓補,如:
you may depend on them to be there early.
the party calls on us to increase production and practise economy.
常這樣用的短語動詞有:ask for, care for, call on, count on, depend on, wait for, long for(渴望), prepare for, wish for等.
⒉作主語補足語
不定式作主語補足語,和主語構成一種邏輯上的主謂關係.如:
①he was not allowed to enter the classroom for being late.
②the young university student is considered to have great promise.
六,不定式作狀語
⒈作目的狀語
(1) ①i stayed there to see what would happen.
②henry has decided to go to the hospital to be examined by the doctor.
(2)有時為了強調,不定式前可加in order或so as.如:
bob took down my telephone number so as(in order)not to forget it.
有時為強調目的狀語可把in order to或不定式置於句首,但so as to不能這樣用.在這種句式中不定式部 分可轉換為so that, in order that, 成為目的狀語從句,如:
i stayed there so that (in order that)i could see what would happen.
(3)在部分表示感情色彩的形容詞,過去分詞或動詞之後可接不定式,如:astonished, glad, happy, laugh , pleased, sad, smile, sorry, surprised等.
①we are glad to hear the news.
②i was surprised to see that a three-year-old baby could write so well.
在部分形容詞後接不定式,用主動形式表示被動意義,這種句型中的主語是不定式的邏輯賓語.如:the question raised by the student is difficult to answer.
the room is really comfortable to live in.
常這樣用的形容詞有:comfortable, easy, dangerous, difficult, expensive, fit, impossible等.
⒉作結果狀語
we came home after our holiday to find our garden neat and tidy.
不定式作結果狀語還常用在下列句式中.如:
①so…as to; such…as to
i'm not so stupid(a fool) as to put it in writing.我不至於愚蠢到會把它寫下來.
i'm not such a stupid fool as to put it in writing.
②enough…to
the speed is high enough for us to catch up with the first liner.
③only to
jane hurried back only to find her mother dying in the hospital.
④too…to
i'm too tired to stay up longer.
但在下列結構中,too…to並非是"太……而不能……"之意.如:
①i'm only too glad to have passed the exam.考試及格我太高興了.(too修飾glad to have…,相當 於very)
②we have too much to learn.我們要學的太多了(不定式作定語).
⒊不定式短語還可作獨立成分,用於句首,句中或句末.如:
to tell the truth, the play was a great disappointment tome.
常見的短語有to be exact(確切地說),to begin with(首先),to do him justice(說句對他公道的 話),to be sure(真的)等等.
七,動詞不定式,動名詞的其它用法
⒈疑問詞+不定式結構
疑問詞who, what, which, when, where, whether, how後可接不定式構成不定式短語,在句中作主語,賓語,表 語等.如:
①when to leave for london has not been decided yet.
②mr. smith didn't know whether to leave or stay there.
③i asked professor xu how to learn english well.
④the question was where to get the medicine needed.
以上例句中疑問詞+不定式部分,均可轉換為相應的從句形式.如:①when we shall leave…③…how i
could learn…
經常在這種結構中使用的動詞有:consider, decide, discover, explain, find out, forget, hear, know, lea rn, observe, understand, wonder等.
⒉動詞不定式的時態,語態
(1)時態
①一般式:動詞不定式一般式表示的動作發生在謂語動詞之後,有時表示同時發生.如:
i hope to become a university student this year.(to become發生在hope之後)
we often hear dick play the piano in the next room.(play和hear同時發生)
②完成式:表示的動作發生在謂語動詞所表示的動作之前.如:
i'm sorry to have kept you waiting.
we are too young to have seen the old society.
③進行式:表示的動作與謂語動詞同時發生.如:
the teacher happened to be correcting our papers when i came in.
they seemed to be discussing something important.
(2)語態
如果動詞不定式的邏輯主語是這個不定式所表示的動作的承受者,不定式一般要用被動語態形式.如:
it's a great honour to be invited to mary's birthday party.(不定式作主語)
it was impossible for lost time to be made up.(不定式作主語)
i wish to be sent to work in the country.(不定式作賓語)
can you tell me which is the car to be repaired (不定式作定語)
he went to the hospital to be examined.(不定式作狀語)
在there be結構中,修飾主語的不定式可用被動,也可用主動.如:there are still many things to take care of (to be taken care of).但有時兩種形式表達的意思不同,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動名詞的時態,語態
(1)時態
①一般式:動名詞的一般式所表示的動作可以是泛指,也可與謂語動詞同時發生,或發生在謂語動作之前 ,之後.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完成式所表示的動作發生在謂語動詞之前.如:
imagine having travelled on the moon.
we were praised for having finished the work ahead of time.
(2)被動語態
①如果動名詞的邏輯主語為動名詞所表示的動作的承受者,動名詞要用被動語態,動名詞的被動語態有一 般式與完成式之分.如:
the young man came in without being noticed.
he prided himself on having never been beaten in class.
②有些動詞後的動名詞用主動形式,但表示被動意義.如:
the bike needs repairing.
if a thing is worth doing, it is worth doing well.
⒋在口語中,為避免重複,常用"to"代替不定式結構,有時甚至可以把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等也常用於這一結構中.
⒌在why引起的問句中,省略"to".如:
why spend such a lot of money
why not wait for a couple of days
⒍當兩個或更多作用相同的不定式並列使用時,只在第一個不定式前加"to".如:
it's quite necessary for us to read more and have more practice.
⒎"to"在下列短語中是"介詞",後接動名詞或名詞形式.如:
devote…to, face up to(勇敢地面對),look forward to(盼望),object to(反對),take to(養 成習慣,對……感興趣;開始從事某種活動),be used to(習慣於)等.