②My chief purpose is to point out the difficulties ofthe matter. ③What I would suggest is to put off the meeting.
当主语和表语都是不定式时，其含义一是条件，一是结果（例①）。当主语是aim,duty,hope,idea,mista ke,plan,purpose,suggestion等为中心词的名词词组（例②）时，或以what引导的名词性分句（例③），不定 式说明主语的内容。
④Our work is serving the people.
⑤What he likes is taking a walk after supper. ⑥The story told by Mr.Wang is interesting.
④⑤句动名词作表语，与主语部分可以转换，如Serving thepeople is out work,而⑥句中是现在分词作 表语，说明主语的性质、状态，现在分词具有形容词的各种特征，另外，动名词作表语还应与进行时态区别开 来。 四、作定语 ⒈不定式作定语
不定式在句中作定语，置于被修饰的名词或代词之后。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. 不定式短语作定语和被修饰词之间表示以下关系： (1)表示将来的动作（例①）。
(2)与被修饰词之间有动宾关系，如是不及物动词，则需加介词（例④）。
(3)与被修饰词之间有动宾关系，同时与句中其它词之间又有逻辑上的主谓关系时，尽管有被动含义，却仍 用主动语态（例③）；如只有动宾关系，而无逻辑上的主谓关系，则需用被动语态（例②）。 (4)不定式作定语时，一般可转换为定语从句，例①to arrive=that will arrive。 ⒉动名词作定语
①This passage can be used as listening materials. ②The reading room of our school library can hold 800people. ③All moving bodies have energy.
①②句动名词作定语说明一种性能，即：用来……的；第③句为现在分词作定语，单个分词作定语常置于 被修饰词之前，与被修饰词之间，可构成逻辑上的主谓关系，分词短语作定语常置于被修饰词之后。如：The man standing at the school gate is Professor Hua. 五、不定式作补足语 ⒈作宾语补足语
一些及物动词除要求按宾语外，有时还需要有宾语补足语，说明宾语的行为、状态、特征，这时意思才相 对完整。
(1)常要求不定式作宾补的动词有：allow,ask,advise,beg,cause,drive（强迫），encourage,expect,fo rbid,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)部分动词后常接to be＋形容词、名词短语等形式，有时to be可省略，如：believe,consider,discov er,find(=consider),feel(=think),imagine,judge,know,prove,think,suppose,see(=understand),understa nd等。 ①We all believe John(to be)honest.
②I consider him(to be)one of the best biology teachers of No. 1 Middle School.
但当不定式是完成式时，to不能省略，如：We consider him tohave been foolish. (3)感觉动词和使役动词后用作宾补的不定式须省略to。 ①I didn't hear anyone say anything about it.
②They make the students do too much homework every day.
这种句式在变为被动语态时，to不能省略，如第②句：Thestudents are made to do too much homework every day.
(4)help,know后面的\可有可无。如： Would you please help me(to) fill in the taxform?
I've never known her(to)be late before.但：He was known to have been to France before. (5)部分短语动词后，常接不定式作宾补，如： You may depend on them to be there early.
The Party calls on us to increase production and practise economy.
常这样用的短语动词有：ask for,care for,call on,count on,depend on,wait for,long for（渴望）， prepare for,wish for等。
⒉作主语补足语
不定式作主语补足语，和主语构成一种逻辑上的主谓关系。如： ①He was not allowed to enter the classroom for being late. ②The young university student is considered to have great promise. 六、不定式作状语 ⒈作目的状语
(1) ①I stayed there to see what would happen.
②Henry has decided to go to the hospital to be examinedby the doctor. (2)有时为了强调，不定式前可加in order或so as。如： Bob took down my telephone number so as(in order)not toforget it.
有时为强调目的状语可把in order to或不定式置于句首，但so as to不能这样用。在这种句式中不定式部 分可转换为so that,in order that,成为目的状语从句，如： I stayed there so that (in order that)I could see whatwould happen.
(3)在部分表示感情色彩的形容词、过去分词或动词之后可接不定式，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.
在部分形容词后接不定式，用主动形式表示被动意义，这种句型中的主语是不定式的逻辑宾语。如：The question raised by thestudent is difficult to answer. The room is really comfortable to live in.
常这样用的形容词有：comfortable,easy,dangerous,difficult,expensive,fit,impossible等。 ⒉作结果状语
We came home after our holiday to find our garden neat and tidy. 不定式作结果状语还常用在下列句式中。如： ①so…as to;such…as to
I'm not so stupid(a fool) as to put it in writing.我不至于愚蠢到会把它写下来。 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 thefirst liner. ③only to
Jane hurried back only to find her mother dying inthehospital. ④too…to
I'm too tired to stay up longer.
但在下列结构中，too…to并非是“太……而不能……”之意。如：
①I'm only too glad to have passed the exam.考试及格我太高兴了。（too修饰glad to have…，相当 于very） ②We have too much to learn.我们要学的太多了（不定式作定语）。 ⒊不定式短语还可作独立成分，用于句首、句中或句末。如： To tell the truth,the play was a great disappointment tome.
常见的短语有to be exact（确切地说），to begin with（首先），to do him justice（说句对他公道的 话），to be sure（真的）等等。
七、动词不定式、动名词的其它用法 ⒈疑问词＋不定式结构
疑问词who,what,which,when,where,whether,how后可接不定式构成不定式短语，在句中作主语、宾语、表 语等。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.
以上例句中疑问词＋不定式部分，均可转换为相应的从句形式。如：①When we shall leave…③…how I could learn…
经常在这种结构中使用的动词有：consider,decide,discover,explain,find out,forget,hear,know,lea rn,observe,understand,wonder等。 ⒉动词不定式的时态、语态 (1)时态
①一般式：动词不定式一般式表示的动作发生在谓语动词之后，有时表示同时发生。如： I hope to become a university student this year.（tobecome发生在hope之后） We often hear Dick play the piano in the next room.（play和hear同时发生） ②完成式：表示的动作发生在谓语动词所表示的动作之前。如： I'm sorry to have kept you waiting.
We are too young to have seen the old society. ③进行式：表示的动作与谓语动词同时发生。如：
The teacher happened to be correcting our papers when Icame in. They seemed to be discussing something important. (2)语态
如果动词不定式的逻辑主语是这个不定式所表示的动作的承受者，不定式一般要用被动语态形式。如： It's a great honour to be invited to Mary's birthday party.（不定式作主语） It was impossible for lost time to be made up.（不定式作主语） I wish to be sent to work in the country.（不定式作宾语） Can you tell me which is the car to be repaired?（不定式作定语） He went to the hospital to be examined.（不定式作状语）
在There be结构中，修饰主语的不定式可用被动，也可用主动。如：There are still many things to t ake care of (to be taken care of).但有时两种形式表达的意思不同，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动名词的时态、语态
(1)时态
①一般式：动名词的一般式所表示的动作可以是泛指，也可与谓语动词同时发生，或发生在谓语动作之前 、之后。如：
We are interested in collecting stamps.
I shall never forget seeing the Great Wall for the firsttime. We are not afraid of dying.
②完成式所表示的动作发生在谓语动词之前。如： Lmagine having travelled on the moon.
We were praised for having finished the work ahead of time. (2)被动语态
①如果动名词的逻辑主语为动名词所表示的动作的承受者，动名词要用被动语态，动名词的被动语态有一 般式与完成式之分。如：
The young man came in without being noticed. He prided himself on having never been beaten in class. ②有些动词后的动名词用主动形式，但表示被动意义。如： The bike needs repairing.
If a thing is worth doing, it is worth doing well.
⒋在口语中，为避免重复，常用\代替不定式结构，有时甚至可以把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等也常用于这一结构中。 ⒌在why引起的问句中，省略\。如： Why spend such a lot of money? Why not wait for a couple of days?
⒍当两个或更多作用相同的不定式并列使用时，只在第一个不定式前加\。如： It's quite necessary for us to read more and have morepractice. ⒎\在下列短语中是“介词”，后接动名词或名词形式。如：
devote…to,face up to（勇敢地面对），look forward to（盼望），object to（反对），take to（养 成习惯，对……感兴趣；开始从事某种活动），be used to（习惯于）等。
英语动名词
动名词是一种非谓语动词形式。它是由动词原形 + ing 构成，同现在分词 形式一样，在句中可作主语，宾语，表语和定语。
1) 动名词作主语：
Talking like that is not polite. 那样谈话不礼貌。
2) 动名词作表语
Seeing is believing. 眼见为实。
3) 动名词作宾语
有些动词须用动名词来作宾语,它们是begin, mind, suggest, finish, stop, need, enjoy, miss, keep.
Please stop smoking in the house. 请不要在家里抽烟。 She is found of collecting stamp. 她喜欢集邮。
4) 动名词作定语
She is studying in the reading room. 她在阅览室学习。
动名词的时态：
动名词的一般时表示动作与句中谓语动词的动作同时发生，或在谓语动词的动 作之后发生。
I enjoy swimming in the big river. 我喜欢在大河里游泳。
动名词的完成时表示动作在谓语动词动作之前发生。
Do you remember having promised me that? 你记得给我许愿了吗？
动名词的被动形式：当动名词和它的逻辑主语是被动关系时，用动名词的被动 形式来表示。
His being looked down upon made him sick. 他被人冷落使他很伤感。
动名词的几个特殊情况：
1) 有些动词的后面能跟动名词做宾语，有些动词能跟不定式，有些两者都可以 它们的具体含义有时还不一样。
能跟动名词的动词有 avoid, consider, delay,
deny, dislike, endure, enjoy, escape, forgive, finish, imagine, keep, mind, pardon, prevent, resist, suggest, understand, can't help 等。
能跟不定式的动词有 decide, desire, expect, hope, mean, pretend, promise, refuse, undertake, want, wish, agree, manage 等。