动词不定式(The Infinitive)
动词不定式：（to）+ do，具有名词、形容词、副词的特征。
一、不定式的形式：
主 动 被 动
一般式 to do to be done
进行式 to be doing /
完成式 to have done to have been done
完成进行式 to have been doing /
否定式：not /never + (to) do
二、不定式的句法功能：
1.作主语：
eg.)To make a speech here is an honor.
To lose heart means failure.
动词不定式短语作主语时，常用形式主语it作形式主语，如上两句可用如下形式：
It is an honor to make a speech here.
It means failure to lose heart.
常用结构：
It+be+ adj./n.+ for sb. to do sth.
It+be+ adj. + of sb. to do sth. =sb. be + adj. + to do sth.
(常见形容词:clever, silly, foolish, stupid, wise, kind, rude, impolite, careless, cruel, crazy, etc.)
Eg.)It’s necessary for us to have a good knowledge of English.
It is foolish of you to make such a mistake.=You are foolish to make such a mistake.
2.作表语：
eg.)Her wish is to become a novelist.
He appears to have caught a cold.
不定式一般紧跟在系动词如be, seem, remain, appear等后面,用来说明主语的内容。这类结构中的主语一般为名词，如：idea, purpose, hope, plan, intention, wish, dream, etc.
eg.) My purpose is to teach them a lesson.
有时句子主语也可以是不定式或名词性从句。
Eg.) To be strict with students is to be responsible to them.
What I want to do is (to )tell you the truth.
如果主语中含有do的任何形式, 那么不定式可以省去to.
Eg.) The only thing he could do was ( to) tell the truth.
比较:
A组: Sth.+be +不定式(作表语)---表示主语的具体内容
Sth.+be +不定式(作表语)---表示时态(将来时)
Eg.)He is to tidy up the room.
His plan is to tidy up the room.
B组:动名词和不定式在句中作表语的区别:
1. 一般情况下,区别不大,可通用
eg.) Seeing is believing.
=To see is to believe.
2. 动名词表示的动作较抽象、或是习惯性的, 而不定式表示某次具体的动作.
Eg.)My job is typing papers.
My job now is to type these papers.
3.作宾语：
A. 动词+ to不定式
常见动词: hope, wish, long, want, refuse, pretend, promise, agree, aim, decide, expect, offer, fail, plan, learn, manage, intend, desire, etc.
eg.) I longed to become an artist.
He helped (to) bring up the orphan.
B.动词+(间接宾语)+疑问词+ to不定式
常见动词: know, decide, wonder, learn, remember, understand, find out, etc.
eg.) I don’t know what to say to comfort her.
The farmer showed us how to milk the cow.
C.动词+ it+宾语补足语+( for sb.)+ to不定式：
常见动词:find, consider, think, make, feel, etc.
eg.) Marx found it important to study the situation in Russia.
I think it important for you to recite some English articles.
D.介词but, except后可接to不定式作宾语。
注意句中谓语或非谓语部分含有do，那么不定式可省去to
eg.)Seeing the room crowded, I had no choice but to stand in the dark.
Seeing the room crowded, I could do nothing but stand in the dark.
4.作宾语补足语：
A. 动词/动词词组+宾语+to不定式
常见动词: want, wish, ask, tell, order, beg, allow, permit, help, advise, persuade, cause, force, warn, invite, urge, encourage, prepare, call on, would like, wait for, etc.
eg.)I got them to join us in the discussion.
They are waiting for the school bus to come.
B. 动词+宾语+不带to的不定式
常用动词: feel (一感) ; hear, listen to(二听); make, let, have(三让); see, watch, observe, notice, look at(五看) ;help (半帮助,可带to或不带to)etc. 但改为被动语态时，不定式要加to.
Eg.) I saw him cross the road.
He was seen to cross the road.
比较: I saw him crossing the road.
He was seen _____the road.
I saw him carried downstairs.
He was seen ____ downstairs.
5.作定语：(考点集中在动词不定式与被修饰词的逻辑关系的判断上)
A.与被修饰名词构成动宾关系：
Eg.) I have a meeting to attend.
He found a good house to live in. (如果不定式是vi，其后应有适当的介词.)
如果不定式修饰time, place, way，可以省略介词：
eg.)He has no place to live.
This is the best way to work out this problem.
注意如果句子的主语不是不定式的逻辑主语,不定式就用被动语态表示。比较:
I am going to the post office, for I have a letter to post.
I am going to the post office, do you have any letter to be posted?
B. 与被修饰名词构成主谓关系：
Eg.)He is the right person to do that job.
He is the first to get here.
注意不定式+介词修饰名词也可以转换成介词+关系代词（whom或which）+不定式。
Eg.) Mary is a nice companion to travel with.
Mary is a nice companion with whom to travel.
I got a piece of paper to write on.
I got a piece of paper on which to write.
C．说明所修饰名词的内容：
Eg.) We have made a plan to finish the work.
Jane expressed a wish to earn her own living.
6.作状语：
A.表目的：
Eg.) He worked day and night to pay off the debt .
She sold her hair to buy the watch chain.
注意不定式逻辑主语与句子主语要一致：
To save money, every means has been tried. (×)
To save money, he has tried every means. (√)
= He has tried every means in order to/so as to save money.
= In order to save money, he has tried every means.
B.表结果：
Eg.)I visited him only to find him out.
Would you be so kind as to tell me the way to the garden Hotel?
His behavior is such as to make his friends angry.
The patient is strong enough to walk about.
too…to…结构
Eg.)It’s too dark for us to see anything.
The question is too simple for him to answer.
注：对少数几个表示心情或倾向的形容词，如：glad, ready, pleased, willing, anxious, happy, satisfied, etc.用于too…to…结构时表示肯定意义。
eg.)They were too anxious to leave.
I am only/but too glad to do you the favor.
C.表原因：
Eg.)They were very excited to hear the news that their team had won the game.
7.作插入语和同位语：
常见插入语:to tell (you) the truth/to be frank; truth to tell实不相瞒;to start/begin with; to conclude; to make matter worse; to be more exact确切地讲;to make a long story short长话短说，简而言之;to be fair公平地说，凭心而论;to be sure肯定地，毫无疑问地;
eg.)To tell (you) the truth, I don’t like the way _______he talked.
To make matter worse/___ ____, the computer broke down.
We have made a plan to finish the work.
Her wish to be an air hostess has never come true.
三、不定式的时态:
1.一般式－(to)+动原：不定式的一般式所表示的动作或状态与谓语动词动作同时发生或发生在谓语动词动作之后。
Eg.)The policeman made the thief stand in the corner.
The play is said to be made into a film soon.
2.进行式－to be+现分：不定式的进行式所表示的动作或状态与谓语动词动作同时发生。(seem, appear, happen, pretend等动词的结构中)
Eg.)The boy pretended to be working hard.
=The boy pretended that he was working hard.
He seems to be reading in his study.
=It seems that he is reading in his study.
3.完成式－to have +过分：不定式的完成式表示的动作或状态发生在谓语动词动作之前.
eg.)I regretted to have told a lie.
I happened to have seen the film.
The novel is said to have been translated into several foreign languages.
=It is said that the novel has been translated into several foreign languages.
比较: I must be off now. I am pleased to have met/meeting you all.(分手告别时)
Pleased to meet you, Mr. Cook.(初次见面时)
四、不定式的语态:
主动式和被动式
A. 如不定式的逻辑主语是动作的承受者, 不定式需用被动语态－to be +过分
eg.) He dislikes to be praised in public.
The only animal to be seen in the desert was the camel.
B. 主动的形式表示被动:
①句中存在不定式的逻辑主语, 构成逻辑上的主谓关系：
eg.) The master gave his dog a few bones to eat.
I have a lot of papers to type.
(比较:I am free now. Do you have any papers to be typed?)
②在“形容词+不定式”结构中, 如不定式与句子主语构成逻辑上的动宾关系,那么不定式多用主动语态.
常见形容词：hard, difficult, easy, fit, cheap, expensive, interesting, etc.
Eg.) The water is fit to drink.
The couch is comfortable to sit on.=It is comfortable to sit on the couch.
The sentence is easy _____ (explain). =It is________
The tea is bitter _______(taste).
③在there be结构中,倾向于用不定式主动语态表示被动意义.
Eg.) There is always much work to do in the house.
④下列句子惯用不定式主动语态.
Eg.) The house is to let/to be let. 这房子待出租。
He is not to blame. 他不该受责备。
但在be + to不定式以及be likely to结构中，如果主语是不定式所表示的承受者，那么不定式仍须用被动语态。
Eg.) The collection of poems is to be published within a year.
The results of the exams remain to be seen.
He is likely to be made monitor of our class.=It is likely that he is made ….
五、不定式的否定式： not/never + (to ) 不定式
eg.) They hurried along in order not to be late.
The boy promised never to play truant again.
六、不定式的省略与保留：保留to,省略do动词。
Ⅰ.不定式符号的省略与保留:
1. 在had better, would rather, would rather…than…, would sooner…than…, cannot but, why (not) 等结构后面的不定式符号to通常被省略。如:
eg.) You’d better tell her the truth.
2. 动词不定式短语作介词but, except, besides的宾语，且介词之前有行为动词do或其它形式时，不定式符号to通常被省略。
Eg.) What do you like to do besides swim?
My mother could do nothing but wait for the doctor to arrive.
Now he had given himself no choice but to tell her.
3. 两个或多个不定式短语表示并列关系时，后面不定式短语的不定式符号to通常被省略；如果表示对比关系，则不定式符号to通常保留。
eg.) They didn’t tell me whether to go on or to stop. （对比关系）
She told the child to stay there and wait till she came back. （并列关系）
4．在某些感官动词或使役动词（如：hear，listen to， notice，observe， see， watch， make等）之后充当宾语补足语
的不定式中，不定式符号to总是被省略， 但在被动语态的句子中，不定式符号to通常保留。
Eg.) They made that man work all the morning.
That man was made to work all the morning.
5.不定式短语作表语，不定式符号to通常保留，但当what引导的名词性从句作主语，或all，everything等后接定语从句作主语，从句谓语部分含有动词do 或do的其他形式时，作表语的不定式可以保留也可省略不定式符号to。
eg.) The greatest happiness is to work for the happiness of all.
The only thing I can do is (to) go on y myself.
II.不定式符号后面动词的省略与保留
1.为了避免重复，在hope， wish， want， like， love，decide， mean， prefer， have to， be able to， be going to， used to， ought to等动词及习语后面出现与上文相同的不定式时，常保留不定式符号to，而把其它部分省略。
Eg.) Ms King lied to us because she had to.
2.当不定式在ask, advise, persuade, wish, allow, permit, tell, expect, force, invite, beg等动词后面充当宾语补足语时, 为了避免重复, 常保留不定式符号to，而把后面的动词省略.
eg.) She wants to come , but her parents won’t allow her to.
If he doesn’t want to go there, don’t force him to.
He didn’t come, though we had invited him to.
3.在特定的上下文中, 为了避免重复, 如果不定式为一般式to be…或完成式to have done时, 则不定式符号to和be或have常一并保留, be或have之后的部分通常要省略.
eg.) ---Aren’t you the headmaster?
--- No, but I don’t want to be.
--- Hasn’t he finished the report?
--- No, but he ought to have.
补充:
不定式符号后面动词的省略与保留：
Eg.)1. If you don’t want to do it, you don’t need to.
2.---Ought I to finish the work today?
---Yes, you ought to.
注：㈠以上例句中的不定式符号to均不能省略。但如省略名词后的不定式时，则to可以一起省去。
Eg.) Never will Tom miss school for no reason; he hasn’t the courage (to).
I will come as soon as I have got the chance (to).
㈡ want 和would like如用于从句中，to通常可以省略。
Eg.) Come whenever you want (to).
You can stay here as long as you like (to).
㈢如不定式带有系动词be或助动词have, 则须保留be或have.
Eg.) ---Are you a teacher?---No, but I used to _be_.
--- Sorry, I haven’t finished my work yet?---Well, you ought to have.
㈣另外两种省略to的情况.
⑴ 如主语部分含有动词do,则作表语的不定式可省略to
eg.) What I want to do is run a night school.
⑵当两个或两个以上的不定式并列使用时,除第一个不定式以外,其余的不定式一般要省略to.
Eg.) It is up to you to decide whether to stay or leave.
He wished to study medicine and become a doctor.