1. 不定式 ( Infinitive )
从本节开始，和接下来的两节，我们要就这类"不能独立地在句中充当谓语的动词或动词形式"分别地进行讨论。这类动词和由它们所构成的动词短语有这样几个共同的特征：

# 它们都是从动词变过来的，虽不能独立地在句子里担当谓语，却可以直接充当（除谓语外）其他各种成分，如：主语，宾语，表语，定语，状语，补足语等。也就是说，它们可以起名词、形容词、副词等作用。
## 由于它们都是从动词变过来的，所以它们依然保留着"动词的某些特征"--它们可以带有自己的宾语、状语。

我们先讨论一下不定式的句法功能，既不定式在句子中能担当那些句子成分。

1）主语
不定式作主语所表达的主要意思是"（要是去）做某事……"。那就是说，它尽管在此间相当于名词、代词的作用，但是它的动作意义却依然很强。另外，在正式的书面文体中，如果是不定式作句子的主语，那么要将不定式后置，而用引导词it 来取代它的"主语位置"。It 在句中没有任何意义，是句子的"形式主语"；真正的"逻辑主语"还是不定式。例如：
To get there by air will take you only about two hours.
乘飞机去那儿记将只花你两个小时。
It will take you only about tow hours to get there by air.
乘飞机去那儿记将只花你两个时。
To do it once more needs time .将这件事再做一遍需要时间。
It needs time to do it once more. 将这件事再做一遍需要时间。

另外，如果要说明不定式短语的"逻辑主语"是谁，可在不定式前面加for引导的短语；在某些形容词作表语时，则要用以of引导的短语（这类形容词常见的有：kind , good , nice , wise , unwise , clever , silly , wrong , right , foolish , stupid , careless , considerate , rude , naughty , impolite）。例如：
It is difficult for him to finish the work within one week.
让他在一周内完成这件工作是很困难的。
It is a pleasure for us to take part in the conference.
对我们来说，参加这个会议是件快事。
It is very kind of you to have given us so much help .
你给予我们这么多的帮助，真难为你了。
It is foolish of them to turn down the proposal .
他们拒不采纳那个建议是愚昧的。

2) 表语
不定式作表语所表达的主要意思是"说明或解释主语（要去）做什么事"。例如：
Her best wish is to put her knowledge into practice.
她最大的愿望是将自己的知识用于实践。
His plan is to make a reform in their teaching methodology.
他的计划是要对他们的教学方法进行改革。
They appear to have accomplished their experiment.
他们似乎已成功地做完了试验。

3) 宾语
不定式可作及物动词的宾语，也可作介词的宾语；这类及物动词常见的有：
advise (忠告) , agree (同意) , ask (请、要) , attempt (试图) , begin (开始) , care (想要) , choose (决定、要) continue (继续) , decide (决定) , desire (希望) , determine (决心) , expect (期望) , forget (忘记) , fail (未能) , hate (不喜欢) , hope (希望) , intend (打算) , learn (学习) , like (喜欢) , manage (设法) , mean (打算) offer (愿意) , plan (计划、打算) , prefer (宁愿) , pretend (假装) , refuse (拒绝、谢绝) , show (演示) , start (开始) , tell (告诉) , teach (教) , try (尽力) , undertake (保证、担保) , volunteer (自愿) , want (想要) , wish (希望)等等。例如：

She learned to cook when she was young .
她年青的时候就学会做饭了。
His father promised to take him to Italy this summer.
他父亲答应今年夏天带他去意大利。
The girl showed us how to dance disco.
那位女孩给我们演示怎样跳迪斯科。
I didn't expect to win the first place in the competition.
我没想到会在比赛中获得第一名的。
They undertook to finish the work by Monday.
他们保证在星期一以前完成工作。
He didn't know whether to laugh or to cry when he heard the news.
他听到那个消息啼笑皆非。
I'd like to advise you what to do. 我要给你出主意怎么办。

4) 定语
英文中有很多名词能用不定式来作它们的定语，这些名词的"动词或形容词形式"后也常接不定式。这种情况可参照上面列举的"常用不定式作宾语的动词"情况。例如：

He agreed ( v. )to join us .他同意和我们一起干。
We reached an agreement ( n. ) to the work together .我们达成协议共同干这工作。
She is able ( adj. ) to speak four languages .她能讲四种语言。
She has an ability ( n.) to speak four languages .她有讲四种语言的能力。
They plan ( v. ) to develop a new product .他们计划研制一种新产品。
They made a plan ( n. ) to develop a new product .他们制订了一个研制新产品的计划。
了解了上述情况后，我们再来看看那些常见的，能用不定式来作它们定语的名词有哪些：
ability (能力，可能) , agreement (同意) , ambition (雄心，野心) , attempt (试，企图) , anything (任何事) , anybody (任何人) , a great deal (许多东西) , anxiety (焦急的心情) , campaign (运动，活动) , chance (机会) , claim (要求，主张) , courage (勇气) , decision (决定) , determination (决心) , effort (努力) , exercise (练习) , eagerness (急切的心情) , failure (失败) , hope (希望) , item (节目) , intention (意图) , man (人) , motive force (动力) , meeting (会议) , nobody (无人) , nothing (无事) , need (需要) , offer (提供、建议) , opportunity(机会) , person (人) , plan (计划) , promise (允诺) , room (房间) , right (权力) , refusal (拒绝、谢绝) , seat (座位) , someone (某人) , something (某事) , struggle (斗争) , time (时间) , thing (事情) , way (方法) , wish (希望)等等。另外，序数词first ，second 等以及last，best，only 等词也常用不定式来作它们的定语。

5) 状语
不定式作状语时，往往是接在不及物动词的后面，修饰谓语动词；表示谓语动作发生的。
A）目的、B）结果、C）原因、D）程度，等等。例如：

A）作目的状语
She came to see me yesterday .她昨天来看我了。
He has been to New Zealand to have his further study. 他曾去新西兰深造过。
The man has to do some part-time jobs in his spare time so as to support his family .那人为了养家不得不在业余时间做些另活。
You should study even harder in order to be a top student.
要当尖子学生，你应更加努力学习。

B）作结果状语
He dwelled so much on the problem only to show his unawareness of the solution to it.
他在这个问题上说了这么一大些，只能暴露出他对解决问题的办法一无所知。
They were too excited to say a word .他们太激动了以至说不出一句话来了。
What she has said to make you so sad? 她说了些什么让你如此伤心？
I returned home that day to find that everything was being in good order .那天我回到家却发现一切会那么井井有条。

C）作原因状语
I am sorry to hear that.听到这事我很难过。
They were surprised to find that nobody was in the house.
发现屋子里空无一人，他们很奇怪。
To see him behaved in that way, I would think that he must have got something wrong with himself .
看到他这样的行为，我想他肯定有点不对劲。

D) 作程度状语
She wouldn't be so silly to say that .她不会傻得去说那件事的。
He was so rude to show the lady his pants.
他粗鲁得将他的短裤给那位妇女看。

6)补足语
不定式作补足语主要是指--不定式在某些动词后面作宾语补足语；当这种含不定式作宾语补足语的句子写成被动结构时，原句中的"宾语补足语"就变成被动句中的"主语补足语"了。在不定式作宾语补足语的结构中，有两种情况：

A）常见的用"带to的不定式作宾语补足语"的及物动词有：
advise (劝告) , ask (请、要) , allow(允许、让) , beg(请求) , cause (使) , command (命令) , compel (强迫) , encourage (鼓励) , expect (预料) , force (迫使) get (让) , hate (不喜欢) , help (帮助) , invite (邀请) , intend (想要) , instruct (指令) , leave (留给) , like (喜欢) , oblige (迫使) , order (命令) , permit (允许) , persuade (劝说) , prefer (宁愿) , press (强求) , remind (提醒) , request (要求) , urge (催促) , warn (警告) , want (想要) , wish (希望)

另外，还有某些短语的后面也可以用这样的复合宾语，这样的成语动词常见的有：
call on (号召), count on (仰仗) , depend on (依靠) , long for (渴望) , prevail upon (说服) , rely on (依靠) , vote for (投票) , wait for (等待) 。例：

I didn't mean you to hear it .我没打算让你听到这事。
He would not like her to go with him .他不愿意她和他一块去。
Don't allow him to come in at this moment.不要让他在这会儿进来。
Tom will get someone to repair your video-recorder.汤姆将找人给你修录像机。
Please remind me to post the letter this afternoon.请提醒我下午把信寄出去。
The students are waiting for the library to open.学生们在等候图书馆开放。
They'll vote for Little Bush to be President.他们将选小布什当总统。
I prevailed him to reconsider his decision. 我说服他重新考虑他作的决定。

B）不带to的不定式作宾语补足语常见的，用"不带to的不定式作宾语补足语"的及物动词有：
feel (感到) , hear (听到) , have (让、使) , help (帮助) , let (让) , make (使) , notice (注意到) , see (看见) , watch (观看) , listen to (听) , look at (瞧、看) 。例如
：
The story made all of us laugh .那故事使大伙都笑了。
Be sure to have him come before dark .一定让他在天黑前回。
Nobody noticed them leave the house .没有人注意到他们离开了屋子。
We listened to him play a piece by Chopin on the piano.
我们倾听他用钢琴演奏肖邦的曲子。
She looked at the cat jump .她瞧着猫跳。

C) 作主语补足语要特别注意作主语补足语的不定式必须带 "to"。例如：
They were even made to work on weekends by the boss.
他们甚至被老板逼得周末都要上班。
We can be depended on to carry on the work.
可以靠我们来进行这个工作。
Someone was heard to open the door .
听见有人开门。
He was finally prevailed upon to take the job.
最后，他被说服接受了这个工作。

我们在前面提到过，不定式没有"表示时间的变化形式"。那就是说，我们仅从不定式本身是无法判断"不定式动作发生的时间"，这种变化形式表现在谓语动词上。但不定式却有"动作进行状态的表达方式"--它们有"进行式"、"完成式"。这种不同"体"的形式是用来表示：不定式动作与谓语动作发生的时间先后关系的。

1) 当我们不强调这种"时间先后关系"时，用不定式的"一般式"。这时在实际意义上， 不定式的动作或是与谓语动作"几乎同时发生"或是"发生于谓语动作之后"。例如：
I didn't hear her say that . ( 几乎同时发生 ) 我没有听见她说那件事。
Mr. Rieder was invited to make a speech at the meeting.
( 发生于谓语动作之后 )里德先生应邀在会议上发言。

2) 不定式的"进行体"强调不定式的动作正在发生，并"与谓语动作同时发生"。例如：
It is very kind of you to be thinking of us .难得你为我们着想。
They seem to be getting along quite well .他们看起来相处得很好。
We surely like everything here to be going well .我们当然愿意这里一切顺利。
He pretended to be listening to the teacher attentively .他假装在专心地听讲。
I'm so happy to be working with you .与你一道工作我很高兴。

3) 不定式的"完成式"则表示不定式的动作业已发生，并"发生于谓语动作之先"。例如：
I regret to have treated her in that manner .我很抱歉用那种态度对待她。
I'm sorry to have left you here alone so long .对不起，让你一个人在这里呆了这么久。
She is said to have published a new book .据说她又出版了一本书。
They seem to have known about it already .他们似乎已经知道了这件事儿。
We happened to have come across the article once .我们碰巧有一次见过这篇文章。

不定式也有"被动式形式"。这种形式主要是说明不定式的逻辑主语与不定式动作之间是"动宾关系"。因此，在决定某个不定式是否使用"被动式形式"之前，必须要根据上下文准确无误地找到、或正确地理解它的"逻辑主语"--也就是不定式动作的执行者。

A) 与不定式相邻的名词、代词可能是不定式的"逻辑主语"，例如：
It is an honour for me to be invited to attend the conference .
应邀出席这个会议是我的荣耀。
She wanted the work to be completed by Friday .
她希望这个工作在星期五以前完成。
He asked to be given a chance to work in the USA .
他申请给他一个去美国工作的机会。
These books are not allowed to be taken out.这些书不得拿出去。
You are invited to banquet to be given at the embassy .
恭请出席在使馆举行的宴会。

B) 与不定式相邻的名词、代词不一定是不定式的"逻辑主语"例如：
He has nothing to do . 他无事可做。
They still have many difficulties to overcome.
他们仍有许多要克服的困难。
We found this accent difficult to imitate.
我们发现这种口音很难模仿。