(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。
不定式的用法
不定式的用法
不定式由“to + 动词原形”构成，其否定形式是“not to + 动词原形”。不定式可以带宾语或状语构成不定式短语，没有人称和数的变化，但有时态和语态的变化。不定式可作主语、宾语、状语、表语和定语，但不能单独作谓语。不定式的逻辑主语有时有“for + 名词或代词宾格”构成。
1．不定式的用法
1）作主语。不定式短语作主语时，往往放在谓语之后，用it作形式宾语。如：
To see is to believe.
It is right to give up smoking.
2）作宾语。不定式短语作宾语时，如果还带有宾语补足语，往往把不定式宾语放在宾语补足语之后，而用it作形式宾语。如：
He wanted to go.
I find it interesting to study history.
有些动词后只能用动词不定式作宾语，必须跟动名词。如：decide，plan，desire，expect，hope, wish，pretend，promise，refuse，afford，agree，ask，fail，tend，pretend，manage
3）作宾语补足语。如：
He asked me to do the work with him.
注意：在feel，hear，notice，observe，see，watch，have，let，make等词后的补足语中，不定式不带to。但这些句子如果变成被动结构时，就必须带to。如：
I often hear him sing the song.
He is often heard to sing the song.
注意：动词不定式在介词but后面时，如果介词之前有行为动词do的各种形式，那么，这些介词后的不定式不带to，否则要带to。另外，在can’t choose but和can’t help but等后面的不定式也省略to。如：
She could do nothing but cry.
I have no choice but to go.
4）作定语。如：
I have some books for you to read.
①作定语的不定式如果是不及物动词，或者不定式所修饰的名词或代词是不定式动作的地点、工具等，不定式后面须有相应的介词。如：
He is looking for a room to live in.
There is nothing to worry about.
Please give me a knife to cut with.
但是，不定式所修饰的名词如果是time，place或way，不定式后面的介词习惯上省去。如：
He had not money and no place to live.
②当作定语的不定式所修饰的名词或代词是不定式动作的承受者时，不定式既可以用主动语态，也可用被动语态，但其含义有所不同。试比较：
Have you anything to send ?
（你有什么东西要寄吗？——不定式to send的动作执行者是“你”）
Have you anything to be seat.
[你有什么要（我或别人）寄的东西吗？——不定式to be sent的动作执行者是“我”或“别人”]
5）作状语，表示目的、原因、结果或条件。如：
I came here to see you. （目的）
We were very excited to hear the news. （原因）
He hurried to the school to find nobody there. （结果）
To look at him, you would like him. （条件）
目的状语还可以用in order to或so as to来表示但so as to不能置于句首。如：
In order to pass the exam, he worked very hard.
We ran all the way so as not to be late.
不定式也可以在作表语用的形容词后面作状语。如：
I am very glad to hear it.
The question is difficult to answer.
“too + 形容词或副词 + 不定式”作状语。如：
He is too old to do that.
另外，句子中有enough这个词时，常用不定式作状语。例如：
The room is big enough to hold us.
6）作表语。如：
My job is to help the patient.
7）作独立成分。如：