一、动词不定式
不定式可作主语、宾语、状语、表语和定语。
1.不定式的时态及语态
to do；to be done；to be doing ;to have done; to have been doing
1).He pretended ____ ______ ___________ a book when I came in.(read)
2).We seem______ ______ ___________ each other before.(meet)
3).He is said______________________ abroad，but I don’t know which country he is studying in.(study)
4).This book is said ______________________ into many languages.(translate)
5).He asked _______________ to work in Tibet.(send)
2.不定式的句法功能
1）作主语：To finish the work in ten minutes is very hard.
动词不定式短语作主语时，常用it作形式主语，例如:
It is very hard to finish the work in ten minutes.
2）作表语：Her job is to clean the hall.她的工作就是打扫大厅。
3）作宾语：常与不定式作宾语连用的动词有：want, hope, wish, offer, fail, plan, learn, pretend, refuse, manage, help, agree, promise, prefer，afford，ask，decide，expect，intend，等。
4）作宾语补足语：
下列动词后跟带to 的不定式作补语：
advise, allow, ask, beg, cause, encourage, expect, forbid, force, get, intend, invite, like, love, order, persuade, prefer, require, teach, tell, want, warn, wish, think, wait for, call on, depend on 等。如：
① An army spokesman stressed that all the soldiers had been ordered ______ _______ clear warning before firing any shots. (issue)
② The teacher asked us ________________________________(不要制造噪音).
③ The flu is believed ____ _____ _________ by viruses that like to reproduce in the cells inside the human nose and throat.(cause)
动词不定式作动词feel,hear，see，watch，notice，observe等感官动词以及have,let，make等使役动词后面的宾语补足语时，不定式符号to要省略。
I saw him cross the road.我看到他过了街道。
He was seen to cross the road.他被看到过了街道。
5）作定语：用不定式作定语的几种情况
①不定式表将来
I borrowed some books to read during my holiday.我借了几本书在假期里读。
②用来修饰被序数词、最高级或no,all，any等限定的中心词。如：
He was the best man to do the job.他是做这项工作的最佳人选。
She was the first woman to win the gold medal in the Olympic Games.
③用于修饰的词是抽象名词时，常见的有：ability，chance，idea，fact，excuse，promise，answer，reply，attempt，belief，way，reason，moment，time等。如：
Do you have the ability to read and write English 你具备读、写英语的能力吗？
④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 got anything to send _____________________________
Have you got anything to be sent _________________________________
⑤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：
Please give me a knife to cut ___________.
Here is some paper for you to write _________.
6）作状语
①表目的: He worked day and night to get the money.为了挣钱，他日日夜夜的工作。
注意不定式放句首时，逻辑主语与句子主语要一致：
为了省钱，能用的方法都用上了。
（×)To save money, every means has been tried.
To save money, __________________________
②表结果He arrived late to find the train gone.他来晚了，结果发现火车开走了。
常用only放在不定式前表示强调：I visited him only to find him out.
③表原因They were very sad to hear the news.听到这个消息他们非常伤心。
3.不定式符号to的保留问题
有时为了避免重复，可以用to来代替前面的不定式，这种情况常出现在下列动词后：expect，hope，wish，mean，prefer，care，forget，want，try以及be glad/happy；would like/love等后面。如：
I haven’t been to Hong Kong，but I wish to. 我没去过香港，但我想去。
—I didn’t tell him the news. 我没有告诉他那消息。
—Oh，you ought to have.你应该告诉他的。
4.动词不定式的几种特殊结构
1）for sb.to do 还是of sb.to do
“for 逻辑主语 不定式”结构称为不定式复合结构，介词可用for或of。当形式主语句型中的表语是形容词，来描述不定式动作时，逻辑主语之前使用for；当它描述不定式的逻辑主语，说明其品质、特征或属性时，要用of，常见形容词有good，nice，clever，wise，foolish，stupid，honest，kind，polite，careful，cruel，brave，crazy等。
2)．疑问词＋动词不定式
疑问词what，which，how，where，when等可以和动词不定式连用，构成不定式短语。“疑问词＋动词不定式”可以作主语、宾语、表语等。
When to start off hasn't been decided yet. (作主语)什么时候出发还没决定。
The question is which bus to take. (作表语)问题是乘哪辆公共汽车。
3). 动词不定式在介词but, other than 后面时，如果介词之前有行为动词do 的某种形式，那么介词后的不定式不带to，否则就要带to。另外在can’t choose but, can’t help but, can’t but 后面的不定式也要省略to。如：
We could do nothing but / other than wait.
We had nothing to do but / other than wait.
We have no choice but to wait.
I can’t choose but laugh.
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