动词不定式是由不定式符号to+动词原形构成,在某些情况下to也可省略。
⒈ 不定式的一般式
不定式的一般式表示的动作通常与谓语的动作同时或几乎同时发生,或是在它之后发生。
如:He appears to be very happy.(同时发生)
To catch the train, we'd better hurry to the station by taxi.(to catch the train发生在hurry to the station之后)
⒉ 不定式的进行式
不定式的进行式表示正在进行的或与谓语动词同时发生的动作。
如:It happened to be raining when I got there.
⒊ 不定式的完成式
不定式的完成式表示的动作在谓语表示的动作之前发生。
如:I'm sorry to have lost your key.
⒋ 不定式的完成进行式
不定式的完成进行式表示的动作在谓语之前发生并且一直进行着。
如:He was said to have been living in London for twenty years.
不定式的时态意义:
如:He is said to be studying abroad.(不定式的进行式表示动作正在进行)
He is said to have studied abroad.(不定式的完成式表示动作已经结束)
⒌ 不定式的被动形式
当不定式逻辑上的主语是这个不定式表示的动作的承受者时,不定式一般要用被动形式。不定式的被动形式根据其与谓语动作发生的先后关系,有一般式和完成时两种。
① 一般式 to be done
如:These are the books to be given out to the students.
② 完成式 to have been done
如:The novel is said to have been translated into many languages.
⒍ 不定式的否定形式
不定式的否定形式由not或never加不定式构成。
如:We decided not to go out because of the bad weather. 由于天气不好,我们决定不出去。
注意:谓语动词的否定和不定式的否定不同的意义
如:I did not promise to wake him up. 我没有答应叫醒他。
I promised not to wake him up. 我答应了不叫醒他。
不定式可以作句子的主语、宾语、宾语补足语、表语、定语、状语等成分。
⒈ 作主语
如:To hear from you is nice.
To be a good teacher is not easy.
不定式作主语时,为了保持句子的平衡,往往以it作形式主语,而不定式置于谓语动词后。
如:It's nice to hear from you.
It's not easy to be a good teacher.
⒉ 作宾语
通常用于afford, agree, aim, arrange, ask, attempt, choose, continue, dare, decide, demand, desire, determine, expect, fail, hate, help, hesitate, hope, intend, learn, long, love, manage, mean, need, offer, plan, prefer, prepare, pretend, promise, prove, refuse, seek, threaten, trouble, wait, want, wish等动词后面。
如:I forgot to lock the door.
Please remember to write to me.
记忆口诀:
三个希望两答应(hope,wish,want,agree,promise)
一个要求莫拒绝(demand,refuse)
设法学会做决定(manage,decide)
不要假装在选择(pretend,choose)
⒊ 作表语
如:My job is to pick up letters.
He seemed to have heard nothing.
⒋ 作定语
在the first, the second, the third, the last等之后通常接不定式作定语。作定语时须放在被修饰的名词之后:
如:He is always the first one to get up.
I have a few words to say on this question.
主动形式表被动含义:
如:I have a book to read.
It is easy to read.
Have you anything to send?
比较:Have you anything to be sent?
She is the last to come.
He is looking for a room to live in.
There is nothing to worry about.
⒌ 作宾补
通常用于advise, allow, ask, beg, cause, challenge, convince, enable, encourage, expect, forbid, force, instruct, invite, order, permit, persuade, recommend, remind, request, require, teach, tell, train, urge, want, warn等词后。
如:He ordered her to leave at once.
He was forced to obey his mother’s order.
⒍ 作状语
不定式作状语时通常表示目的,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。一般说来,用于句首属于强调性用法,即强调动词的目的。也可用于“be adj. to do”结构中作原因状语。
如:He got up early to catch the first bus.
To finish the task on time, we have to work hard.
I'm happy to hear the news.
I'm surprised to see him here.
only to...往往表示“意想不到”的结果;never to...可以接后续的结果。so...as to..., such... as to..., enough to..., only to...以及too...to...等结构中的不定式也表结果:
如:Her father disappeared, never to be heard again.
I went to the bank only to find it was closed.
⒈ 作目的状语。不定式作目的状语,带有很强的目的性,有时可以把(in order) to do置于句首。而现在分词作目的状语时,目的和伴随兼而有之。多放于句末,与主句用逗号隔开。
如:(In order) to ensure success, we must make a complete and through plan.
You should keep it a secret, trying to protect the plan.
⒉ 作结果状语。不定式作结果状语表示意外的结果。现在分词作状语表示自然的结果。
如:He returned home many years later, only to find that everything had changed.(意外的结果)
It rained heavily last night, causing the river to rise.(自然的结果)
⒊ 作独立成分
to be honest, to begin with, to start with, to tell you the truth, to make a long story short
如:To tell you the truth, I told a lie.
To begin/start with, let’s sing a song.
To make a long story short, he succeeded in passing the exam.
⒈ 用it作形式主语
动词不定式作主语时,如果主语太长,通常用it作形式主语,将真正的主语——动词不定式后置。
如:For us to learn English well is necessary.
→It is necessary for us to learn English well.
动词不定式作主语时,如果将句子变为疑问句,应使用it作形式主语。
To walk to the station takes twenty minutes.
→Does it take twenty minutes to walk to the station?
⒉ 用it作形式宾语
某些不能修饰人的形容词作宾语补足语时,不能用表示人的词作宾语,应用it作形式宾语,再用动词不定式的复合结构作真正的宾语;这类形容词常用的有necessary, easy, hard, common, possible及impossible等。
如:父亲的猝死,使得他必须辍学。
误:His father’s sudden death made him necessary to leave school.
正:His father’s sudden death made it necessary for him to leave school.
⒊ 动词不定式作定语时是否要介词
动词不定式与被修饰的名词或代词构成动宾关系时,如果动词不定式的动词及不及物动词,或者该动词不定式本身有宾语,其后面应加上与之用法相应的介词。
如:We are looking for a room to live in.
但被修饰的名词为place, time, way等时,则往往省略介词。
如:That’s a nice place to work(in).
⒋ 不定式主动式和被动式作定语区别
动词不定式作定语时,如果其表示的动作为句子的主语发出时,该动词不定式一般用主动式;如果动词不定式表示的动作不是句子的主语发出的,该动词不定式应用被动式。
如:I am going to the shop because I have something to buy.(“buy”这个动作是句子的主语“I”发出的,故用主动式to buy)
I am going to the shop. Do you have anything to be bought? (“buy”这个动作不是句子的主语“you”发出的,故用被动式to be bought)
⒌ “too...to...”结构
① “too +形容词或副词+ to do”中的动词不定式表示结果,含有否定的意义,意思是“太……以致不能……”
如:The problem was too complicated for us to solve.
② 但下列结构表示肯定含义。
⑴ 当too前或to前有否定词构成双重否定时:
如:English is not too difficult to learn. (英语并不太难学。)
He is too wise not to see that. (他很聪明,不会不懂这一点。)
⑵ 当too后是glad, pleased, happy, delighted, satisfied, ready, willing, kind, apt, good, true, easy, near, careful, well, early, delicious, eager, anxious等形容词或副词时;与这些词连用时,too前还常加上only, all, but, just, simply等副词,意思不变,因为这些词加上too后与very同义。
如:They are too anxious to leave. (他们急于离开。)
He is too ready to help others. (他总是乐于助人。)
I'm only too glad to see you. (见到你非常高兴)
They are too pleased to hear the news. (他们听到这个消息,非常高兴。)
⑶ 与cannot连用:
如:You cannot be too careful (=You can never be careful enough) to do your homework.
你做作业越仔细越好(=无论怎样仔细也不过分).
不定式在句中作定语或真正的主语时:
There are too many problems to be solved. (有很多问题有待解决。)
⒍ in order to与so as to
动词不定式作目的状语位于句首时,前面可加in order,但不能加so as;动词不定式位于句末,则加in order或so as均可。
如:In order to make money, they did anything.
They set out early in order to/ so as to get to the village before 9.
⒎“疑问词+不定式”结构
“疑问词+不定式”结构中的疑问词,包括疑问代词who,what,which和疑问副词how,when,where等。这些疑问词和不定式一起构成了不定式短语,这种结构可在句子中作主语、宾语、表语等。
如:How to do it is a question. (作主语)
I really don't know what to write about. (作动词宾语)
We must first solve the problem of whom to serve. (作介词宾语)
The question is where to put it. (作表语)
I asked him how to learn English. (作宾语补足语)
⒏ 不定式复合结构
不定式可以与其逻辑主语一起构成不定式复合结构,其形式:“for+名词/人称代词宾格+带to的不定式”。其中的名词或人称代词宾格与不定式构成逻辑上的主谓关系。
如:It is important for us to learn English well.
但当表语表示不定式的逻辑主语的特征属性时要用of,如:good, kind, nice, wise, clever, silly, stupid, foolish, right, wrong, rude, impolite, careless
如:It is very kind of you to help me. = you are kind to help me.
⒈ watch, see, notice, observe, look at, hear, listen to, feel, make, let, have后接不定式做宾补时,省略to;但get sb. to do中的to 不能省略。
注意:主动省to的这些句子,变成被动形式时必须加to。
如:I saw him play basketball.
I noticed him come in.
They made me repeat the story.
I was made to repeat the story.
⒉ 当介词but, except, besides之前有一个实义动词do (助动词do及其变化形式除外)时,后面的动词不定式不带to。此外,在can not but/except, can not choose but/except, can not help but/except这三个固定用法中,but/except之后的不定式也不带to。
如:The enemy could not choose but surrender.
I could do nothing except agree to his terms.
Can you do nothing but sell the wedding ring?
⒊ 介词instead of 前后的两个成分要相等。如果前面的成分是不定式,则后面的不定式不带to。
如:He went to play football instead of see a film.
would (had) as soon, had better, had best (不常用) 等之后,不定式省略to。
You had better not smoke.
I’d just as soon come tomorrow.
⒋ 某些惯用法中,than之后的不定式不带to, 如do nothing else than, do more (less) than, do no more than, would (had) sooner than, would rather than等。
如:I would rather not see him.
The old worker often does more than fulfill his quota.
⒌ why引导的省略问句中。口语中,不带to的不定式常在why引导的省略句中作谓语。表示不同意或反驳的意见。
如:Why not give her another chance?
Why bother?
Why not do it yourself?
⒍ make, hear, let, go构成惯用语时,常用省略to不定式。
如:Can't you make do with 10 pounds? 10英磅不可以凑合着用吗?
They let ship the good chance. 他们错过了那次好机会。
The children made believe that they were generals.孩子们假扮成将军。
⒎ 动词go和come之后作状语时省略to:
不定式在动词 go 和 come之后作状语时,在某些情况下总是不带 to。这种用法在祈使句的go 和come之后最常见。在陈述句中也会出现这种用法,但一般在go 和come不发生形态变化的情况下才出现。
如:Go chase yourself!!(走开,别来捣乱!)
Come sit beside me.
You should go thank him.
⒏ 两个或两个以上的不定式并列在一起时,第一个不定式带to,后面的不定式往往把to省去;但表对照时不能省to:
如:I wish to finish my task and (to) get away.
It is better to laugh than to cry.
⒈ 为避免重复,口语中常可省去与前边动词重复的动词原形而留下to。
如:—Would you like to go to the films with me?
—I’d like to.
⒉ 如果不定式to后的结构中含有be, have或have been,通常要保留be, have或have been,但随后的成分仍可省略。
如:—Is your mother a teacher?
—No, but she used to be.
—He hasn’t finished yet.
—Well, he ought to have.