不定式在句中的作用

不定式作主语
* To stop the work now seems impossible. 现在停止工作似乎已经不可能。
* To love and to be loved is the greatest happiness one can seek. 爱与被爱是一个人所能寻找的最大幸福。

很多时候为了避免头重脚轻的现象, 常以it 作为先行词, 而把不定式移到句子的后部。
a) it + be + 形容词 + 不定式
* It isn't right to gossip about others. 说闲话是不对的。
* It is nice not to be dependent on them. 不依靠他们是好的。

b) it + be + 名词 + 不定式
* It‘s our duty to take good care of the old. 照顾好老人是我们的义务。
* It was a pity to have to go without her. 她没能一起去真是可惜。
* It is not a good habit to stay up too late. 熬夜到太晚是个不好的习惯。
* Isn't it a good idea to set up a lab of our own? 建一座我们自己的实验室不是个好主意吗？

c) it + 动词 + 宾语 + 不定式
* It requires a lot of money to build a house. 建一座房子需要一大笔钱。
* It takes five minutes to walk there. 走到那里需要5分钟。
* It seems a pity to refuse. 拒绝似乎是很遗憾的。

d) it + be + 介词短语 + 不定式
* It's beyond me to explain these. 要解释这些我力所不及。
* It's really beyond my ability to communicate with you. 我确实无法和你交流。

2) 不定式作宾语
a) 不定式作宾语
* He neglected to pay the fee. 他忘记付钱了。
* My mother hates to move from place to place, for she feels tired. 我妈妈讨厌搬来搬去，因为她感到很疲倦。
* She failed to finish the assignment in time, and she was worried about it. 她没有及时完成任务，她对此感到很担心。
* I can't afford to buy a car. 我买不起小汽车。
* We will arrange to see him tomorrow. 我们将安排明天见他。
* They preferred not to put this on the agenda. 他们宁愿不把这列入议程。
* I am preparing to take the examination on Monday. 我在准备参加礼拜一的考试。

注： 动词help可有不带to的不定式作宾语。
* Regular exercise will help (to) improve your health. 经常进行锻增进健康。

b) 不定式与连接(代)副词连用构成宾语结构
* I hope you'll advise me what to do. 我希望你给我出主意怎么办好。
* I couldn't decide which book to choose. 我决定不了选择哪本书。
* Could you please tell me where to park my car? 你可以告诉我哪里可以停车吗？
* Have you decided when to marry? 你决定什么时候结婚了吗？
* He didn't know whether to laugh or to cry. 他感到啼笑皆非。
* Everyone has his own idea of how to do it. 如何做这件事各人都有不同的看法。
* Marx gave some advice on how to learn a foreign language. 马克思给了些关于如何学习一门外语的建议。
* I'm worrying about what to do next. 我正在担心下一步该怎么办。

c) 有时可以用 it 作形式宾语，而把不定式后置。
* He found it hard to learn maths. 他发现数学很难学。
* Don't you think it better to translate it this way? 你难道不觉得这样译好些吗？
* I consider it better not to go. 我认为还是不去为好。
* He made it a rule only to speak English in class. 他规定课堂上只能讲英语。
* He regards it as important to help his friends. 他认为帮助朋友是很重要的。

3) 不定式构成复合宾语
a) 许多动词可有不定式作为复合宾语，即: 动词 + 名词 (代词) + 不定式。
* They preferred her not to go with them. 他们宁愿不跟他们去。
* He wants all of us to make rapid progress. 他希望我们大家都迅速进步。
* I didn't expect you to arrive here so soon.我没有料到你会来得这么快。
* What do you advise me to do? 你建议我做什么？
* They invited us to go there in the summer. 他们邀请我们夏天去那里。
* Tell him to come here the day after tomorrow. 告诉他后天到这里来。

b) 作为复合宾语的不定式可以是完成形式或进行形式。
* People consider Charles Babbage to have invented the first computer. 人们认为查尔斯·巴贝奇是第一个发明电脑的人。
* We believed it to have been a mistake. 我们相信那曾是个错误。
* The man was later discovered to have been a spy. 　后来，发现这个人当过间谍。
* Of course we should like everything to be going smoothly. 当然我们愿意一切都进行得很顺利。

c) 有些动词可跟带有to be 的复合宾语。
* The note reminds me to be careful whatever I do. 这小纸条提醒我做什么事都要谨慎。
* What do you consider to be your greatest achievement? 您认为您最伟大的成就是什么？
* We believe him to be guilty. 我们相信他是有罪的。
* We know him to be a fool. 我们知道他是个笨蛋。
* They find the Chinese people to be happy and cheerful．他们发现中国人都很幸福快乐。
* He declared the rumor to be false. 他宣布传闻是假的。

d) 跟复合宾语的动词有时可用被动语态。
* She will be sent to study abroad. 她将要被送到国外读书。
* Tom was considered to be one of the best students in our class at that time. 那时汤姆被认为是我们班上成绩很好的学生之一。
* Money was also thought to be very important. 　　钱也被认为是很重要的。
* Mr. Brown is said to have left for Italy last week. 据说布朗先生上个星期去了加拿大。
* They are said to be building another bridge across the river. 据说他们正在这条河上修另一座大桥。

e) 有些动词只跟不带to 的不定式构成复合宾语。
* He saw her fall from the cliff. 他看见她从悬崖上掉下去。
* I felt someone open my door． 我感觉有人开了我的门。
* He notices a thief slip into the house. 他注意到一个小偷溜进了房子。
* I will have the students write a passage about Internet. 我会让学生写一篇关于网络的作文。
* Her parents let her stay out late. 她父母让她在外面呆到很晚。
* What make you think like that? 是什么使你这样想？
* Please listen to me sing the song again．请听我把这首歌再唱一遍。
* Look at the girl dance! 瞧那些女孩跳舞！

注：动词help 可以跟带to 的不定式作宾语补语，也可以跟不带to的不定式作宾语补足语。但被动时则要加to:
* She sometimes helps her mother (to) wash clothes. 她有时帮她妈妈洗衣服。
* I helped him (to) find his things. 我帮他找东西.
* They were helped to complete the project. 他们得到帮助完成项目。

f) 有些“动词 + 介词”结构后也可跟不定式构成的复合宾语。
* The government calls on the public to fight against piracy. 政府号召大众人民反对盗版。
* We are all longing for the new term to begin. 我们都期待新学期开始。

4) 不定式作定语
a) 不定式可以作后置定语修饰前边的名词
* I have a lot of work to do.　我有很我工作要做。
* He was the first athlete to get to the finishing line. 他是第一个到达终点的选手。
* It's time to get up! 该起床了!
* He made no attempt to carry it out. 他无意将它付诸实行。
* His anxiety to succeed led him study very hard. 他迫切希望成功，这促使他非常努力地学习。

b) 不定式作定语有时会用到被动形式。
* You are invited to a party to be given at 7:00 p. m. Dec. 5. 请你参加将于十二月五日晚上七点举行的晚会。
* Have you got ready for the meeting to be held? 你为即将举行的会议准备好了吗？
* I'm going to the post office. Do you have any letters to be posted? 我要去邮局。你有信要寄吗？

c) 不定式还可以和关系代词which连用作定语 【高中以上】
* It was a bad season in which to have outings. 这是一个不适于郊游的季节。
* Allow me one minute in which to change my costumes. 给我一分钟时间来卸装。
* She had a little money in the bank, with which to help her mother. 她在银行有一点存款，用来帮助她的妈妈。

5) 不定式作状语
a) be + 形容词 + 不定式
* He was delighted to see his old friend again. 他再见到他的老朋友感到很高兴。
* She was afraid to go out at night. 她晚上不敢外出。
* Are we likely to arrive in time? 我们能够及时到达吗？
* John was careless to break the cup. 约翰不小心把杯子摔破了。

b) 不定式作状语可以表示目的、原因、结果等。
* A group of young people got together to discuss this question. 一群年轻人聚集在一起讨论这个问题。
* I often read China Daily so as to improve my reading.我常读《中国日报》以提高我的阅读。
* The whole nation was in deep sorrow to learn the death of Lincoln. 听到林肯去逝的消息，全国都沉浸在悲痛之中。
* She tried to kill herself only to be saved.她企图自杀，后来被救了。

c) 不定式可作状语修饰整个句子。
* To begin with，I do not like its color. 首先，我不喜欢它的颜色。
* To tell you the truth，the film was a great disappointment to me. 说实在的，那部影片使我大为失望。
* To make a long story short，we agreed to disagree. 长话短说，我们同意各自保留不同的看法。
* It happened late last century in 1995, to be exact. 事情发生在上个世纪末—准确地说，在1995年。
* To make matters worse, it started to snow when evening came. 更糟糕的是，天黑时天开始下雪了。

d) 此外，在许多句型中也可用不定式作状语。
* He is too excited to sleep.他太激动了，不能入睡。
* Tom kept quiet about the accident so as not to lose his job. 汤姆对事故保持沉默是为了不丢掉他的工作。
* His indifference is such as to make one despair. 他如此冷淡，令人感到绝望。
* Baker can't have done such a terrible thing as to keep you waiting for so long. 贝克不可能做出这么糟糕的事让你等了这么久。
* Would you be so kind as to carry the luggage for me？你能帮我提一下行李吗？
* People there killed many lions in order to protect the deer. 那里的人们为了保护鹿, 杀掉了许多狮子。
* He was lucky enough to find a seat.他够幸运的，能找到座位。
* He came in quietly in order not to wake the child. 他轻轻地走了进来, 以免吵醒孩子。

6) 不定式作表语
* His wish is to buy a luxurious car in the near future． 他的愿望就是在不久的将来买一辆豪华的小车。
* To learn a language is to use it. 学语言是为了使用语言。
* To see is to believe. 眼见为实。
* What impressed him most was to see the great changes that had happened there. 给他印象最深的是看到那里所发生的巨大变化。