动词不定式(Infinitives)
动词不定式的形式：
一、动词不定式的时态
如果不定式所表示的动作与主要谓语动词所表示的动作同时（或几乎同时）发生或发生在主要谓语之后，通常用不定式的一般形式。如：
I saw him go out. I’m glad to see you.
1.如果不定式所表示的动作发生在主要谓语动词或特定的时间之前，不定式就要用完成式。如：
I intended to have telephoned you, but I forgot to. I should like to have bought a dictionary.
2.不定式进行式表示主要谓语动词所表示的动作发生时，不定式所表示的动作正在发生。如：
I am glad to be talking with you. She pretended to be listening attentively.
3.不定式完成进行时表示的是一个开始于过去某一时刻但一直延续到谓语动词发生的那一时刻
的动作。如：He was thought to have been working on the project for two years.
(1). They pretended not to see us. (一般式表示与谓语的动作同时/几乎同时/发生在它之后.)
(2). He pretended to be sleeping. (在谓语动词发生的同时,不定式的动作也正在进行)
(3). She pretended to have known it before. (完成式表示动作发生在谓语动作之前)
(4). We’re happy to have been working with you.
(完成进行式表示谓语动作发生之前,不定式的动作一直在进行而且可能之后也继续)
二、不定式的被动语态
当不定式的逻辑主语是动作的承受者（和不定式相关的名词或代词与不定式中的代词存在被动关系）时，这个不定式要用被动式，包括它的各种时态在内。如：
She doesn’t like to be treated as a guest. 她不喜欢被当作客人对待。
They want their TV set to be fixed right now. 他们想把电视机马上修好。
There are a lot of things to be done. 有许多事要做。
This is the text to be read next time. 下次就读这篇课文。
注意：to let, to blame这两个不定式在用作表语时，习惯上是用主动形式表示被动意义。如：The house is to let. 这房子要出租。 A lot of work still remains to do. 许多工作有待去做。
动词不定式的用法
1.不定式作主语
⑴原则上，可用动词不定式直接作句子的主语，通常用it作句子的形式主语，而把不定式移到后面，形成“It + 谓语… + 动词不定式…”的句型。若要说明不定式的动作的执行者，可以在不定式前面加上“for + 名词或代词”结构，或是“of + 名词或代词”结构。如：
It is a great pleasure for me to talk with him. It is very kind of you to help me .
2.不定式作宾语
不定式作宾语有两种情况：1）及物动词后直接跟带to的不定式2）“动词+疑问词+带to的不定式”。
（1）“动词+带to的不定式”结构：常见的以不定式作宾语的动词有afford, appear, agree, ask, believe, decide, demand, desire, fail, intend, learn, mean, offer, refuse, wish等。如：I can’t afford to buy a house.
（2）“动词+疑问代（副）词+不定式”结构：常见的这类动词有advise, decide, forget, know, learn, remember, see, tell, think, teach, wonder，discover, understand, guess, explain等。这类疑问代（副）词what, when, which, where, how, whether等（不包含why）。如：
She does not know how to go there. He will tell you how to deal with it.
（3）在不定式作宾语时，有时我们会使用it作形式宾语，而把不定式放到后面。如：
They consider it inappropriate to have classes in the evening.
（4）在tell, advise, allow, forbid, learn, show, decide等词的后面常用“连接词+不定式”作宾语。例如：We must decide whether to go or stay. I don’t know how to get in touch with him.
3. 不定式作定语
不定式作定语相当于一个定语从句，它修饰以下几类名词：
(1) 不定式作定语可用来修饰代词something, anything, everything, nothing.不定式做后置定语。
Do you have anything to send? 你有什么东西要寄吗？（不定式to send的动作执行者是you）
Do you have anything to be sent? 你有什么要（我或别人）寄的东西吗？（不定式to be sent的动作执行者是已被省略的me或someone else）
She has everything to lose and nothing to gain.
(2)由only, last, next, 序数词或形容词最高级修饰的名词后常用不定式作定语。
Jim is the only student to answer the question correctly in his class.
You are the last to undertake the blood test.
(3)不定式常作为定语修饰there be结构的真实主语。在there be结构中，用来修饰主语的不定式有时用主动形式，有时用被动形式。当说话人考虑的是必须有人完成某件事时，不定式用主动形式。如果说话人强调的是事情本身必须被完成时，不定式则用被动形式。例如：
There is a lot of work to do.（Somebody has to do the work.）
There is a lot of work to be done.（The work has to be done.）
(4) 如果不定式中的动词是不及物动词,则不定式中要有介词.
I have something to say. He has a lot of homework to do .
He is looking for a room to live in. There is nothing to worry about.
∴不定式所修饰的名词或代词是不定式动作的地点工具等，即使是及物动词，不定式后面仍须有相应的介词。Please give me a pen to write with.
∴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要省去。
He had no money and no place to live. 他没钱没地方住。
4.不定式作状语
不定式作状语相当于一个状语从句，表示形为的目的、结果或原因。
⑴不定式可以表示目的。在这种情况下，不定式的逻辑主语通常也是全句的主语。
He stayed there to see what would happen.
⑵only to do sth.在句中做结果状语,一般用逗号和句子主干分开,它表示出乎句子主语意料之外的/
不如人意的结果，如：
Many reporters hurried to the airport, only to be told that the superstar had already left.
很多记者匆忙赶到机场,结果只是被告知说那个超级明星已经离开了.
5. 不带to 的不定式
1). 表示感觉的动词五看see，notice，watch，observe，look at三使have，let，make 二听hear，listen to 一感觉feel He noticed the man enter the room.他注意到有人进屋了。
They observed her do the experiment.他们观察她做实验了。
2). rather than, had better, would rather, might as well等之后，不定式不带to. 如：We might as well go without him.我们可以不让他跟去。You’d better go now.你最好现在走。
