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1、不定式的相关用法,一、不定式的概念不定式是非限定动词，不受主语的人称和数的限制。一般由to原形动词构成，有时可不带to。,不定式在句中的用法一、不定式做主语1）To see is to believe.百闻不如一见。2）To obey the laws is important.当作主语的不定式较长时，常用it 做形式主语，而将真正的主语放在谓语之后。如：3）Its important to study hard.注意：当不定式做主语的句子中出现了一个不定式做表语时，不能用it 做形式主语。Its to believe to see . ( x )常见带it形式主语的句型有：Its +adj.
2、 (for/of sb.) to do sth.It takes sb. some time to do sth.,二、不定式做宾语1) 在英语中，不定式可用来做宾语。如：He agrees to go with us. 他同意跟我们一起去。I want to buy a Chinese-English dictionary. 我想买一本汉英词典。 2) 不定式做宾语时须注意：A、不定式并不是可做任何及物动词的宾语。能接不定式做宾语的动词有：afford, agree, arrange, ask, attempt, begin, care, choose, continue, dare, de
3、cide, desire, demand, determine, elect, expect, fail, hate等。如：I cant afford to buy such an expensive computer. 我买不起这么昂贵的电脑。He decided to work in that factory. 他决定去那家工厂工作。,B. 做宾语的不定式如果带有自己的补足语，则须用it做形式宾语，而将真正的宾语置于补足语之后。如：Do you think it necessary to master a foreign language? 你认为掌握一门外语有必要吗？ C. 不定式一般不
4、做介词的宾语，但可做介词but, except的宾语，并且，当but, except前面如果有动词do时，不定式的to须省略。如：He said nothing except to go away. 他一话没说就走了。Now we cant do anything but wait for him. 现在我们只能等待他。,三、不定式做宾语补足语动词接动词不定式做宾语的补足语时，不定式的to不能省略。这样的动词有：advise, allow, ask, beg, cause, encourage, expect, force, forbid, get, help, order, permit,
5、persuade, require, teach, tell, want, wish, warn, call on, wait for, long for。如：The teacher advised us to learn through experiment. 老师劝我们通过实验来学习。They didnt allow us to enter the hall. 他们不允许我们进入大厅。,(2) 动词接动词不定式做宾语的补足语时，不定式的to须省略。即通常所说的，“五看”：notice, see, watch, observe ， look at“三使役”：have, let, make “
6、二听”：listen to, hear“一感觉”：feel“半帮助”：help但它们变为被动语态时，不定式的to不能省略。如：The boss made the workers work over ten hours a day in the past. The workers were made to work over ten hours a day by the boss. 过去老板使工人们每天工作十多个小时。I saw Li Lei fall down from his bike. Li Lei was seen to fall down from his bike. 我看见李蕾从单车
7、上摔了下来。,四、不定式做表语不定式短语可用来做系动词的表语。如：My hope is to become a scientist like Einstein. 我的希望就是做一个像爱因斯坦那样的科学家。My job is to teach English. 我的工作就是教英语。(2) 不定式做表语时须注意两点：一般说来，不定式前面的to不能省略，但当主语部分含有动词do时，to须省略。如：What I want is to visit the History Museum now. 我所想的就是现在去参观历史博物馆。What he wants to do is go swimming in
8、that river. 他想做的事就是去河里游泳。,五、不定式做定语不定式做定语时，一般放在所修饰的名词、代词之后，表示即将发生的动作。如：We have much work to do. 我们有很多事情要做。I have a letter to answer. 我有一封信要回复。(2) 不定式做定语时，中心词与不定式的关系：A. 主谓关系，即：中心词是不定式的逻辑主语。如：Li Chen was the first student to come into the classroom this morning. 今早李晨是第一个进教室的学生。Liu Ying was the very gir
9、l to meet you. 刘英正是来接你的那个女孩子。,B. 动宾关系，即：中心词是不定式的逻辑宾语。如：Do you have anything to do now? 你现在有事情要做吗？I have some clothes to wash. 我有些衣服要洗。当不定式与所修饰的中心词有动宾关系时，不定式中的动词须为及物动词，若是不及物动词，不定式后须加上适当的介词。如：Go ahead, please. I have a friend to wait for here. 请先走吧，我还有个朋友要在这儿等。C. 说明关系，即：不定式是中心词的内容。如：I had a dream to f
10、ly in the sky like a bird. 我做了一个像鸟儿在天上飞的梦I have a wish to go to college. 我有一个上大学的愿望。,六、不定式做状语不定式做状语，可表示动作的目的、结果、原因、条件和方式。A. 表目的表目的时，不定式可放在句子的前面也可放在句子的末尾。但在句子前面时，不定式常与句子用逗号隔开；而在句子末尾时一般不用逗号隔开。如：To get there on time, we set out at five in the morning. 为了按时到达那儿，我们早晨五点就出发了。He goes there to enjoy the fres
11、h air. 他去那儿享受那儿的新鲜空气。比较：to do, in order to do, so as to do都可表示目的，但to do, in order to do的位置既可在句首，又可在句末；而so as to do只能在句末。In order to build a house, he bought some wood and steel yesterday. He bought some wood and steel yesterday in order to build a house. / He bought some wood and steel yesterday so
12、as to build a house. 为了建房，昨天他买来了木料和钢材。,B. 表结果不定式在下列结构中表示谓语动作的结果，不定式的位置一般在句子末尾。表示终结性的动词find, see, hear, learn, discover的不定式，常表示出乎意料的结果，并且，不定式前常有never, only等副词修饰。如：I hurried to the railway station yesterday, (only) to find that the train had left. 昨天我急急忙忙赶到火车站时，发现火车已经开走了。I went to the classroom, to di
13、scover it empty. 我走到教室，结果发现教室是空的。,C. 表原因不定式表示原因时，一般放在句子的末尾，说明主语某种心情、情感(glad, pleased, sad, worried, sorrow, excited) 所产生的原因。如：Im very glad to hear that Li Lei has been elected secretary of the Party. 听说李蕾被选为了党的书记，我很高兴。D. 表条件不定式表示条件时，一般放在句首。如：To be heated, liquid will change into gas. 如果受热，液体就会变成气体。E
14、. 表方式不定式可接在as if / as though之后表示方式时，如：He moved his mouth as if to say something. 他的嘴唇动了动，好像要说什么事似的。,附，课本上的例句： By the middle 1990s, however, industry was making multimillion dollar investments in processing and man-ufacturing technologies specially designed(1) to use recovered materials instead of vi
15、rgin raw materials (2)to produce a broad range of products.（1）做后置定语（2）做目的状语,七、不定式做同位语不定式可用作同位语，说明某些名词或代词task, idea, thought的内容。不定式做同位语时，在名词或代词与不定式之间常用逗号隔开。如：Suddenly I have got the idea, to hunt rabbits in the woods. 突然，我有了这个想法，去林子里去猎取野兔子。八、不定式做独立成分To tell you the truth, I dont like it. 告诉你实话，我不喜欢它。,Thanks for your listening!,
