高中英语动词不定式的用法(二)

动词不定式的用法（一）动词不定式的句法功能：动词不定式在句中可充当主语、表语、宾语、宾补、定语和状语等。

一、作主语：不定式作主语时，通常表示一个具体的，特定的行为。

其谓语动词用第三人称单数形式。

动词不定式作主语可位于句首。

例如：To live means to create.To do that sort of thing is stupid.To learn a skill is very important for everyone in society.但是当作主语的不定式是较长的短语是，我们通常使用it作形式主语，而将动词不定式置于句末。

例如：It is necessary for young students to learn a foreign language.It was his job to repair bicycles(自行车)常用it作形式主语，而用动词不定式作实际主语的常用句型有：1. It is＋adj (＋for sb.／sth.) ＋to do sth.表示“做某事对某人来说怎么样”。

通常表明的是事情对人产生的影响或意义。

比如“难易程度、重要性、可能性大小等”。

用于此句型的形容词有：easy, hard, difficult, possible, important, impossible, necessary, good, bad, exciting, interesting, surprising等。

例如：It is interesting to play this game.It is necessary for you to change your job.How rude it was of the boy to jump the queue!It is friendly of the family to try to make me feel at home in their house.How silly it was of you to give up such a good chance！2. It’s +adj.+of+sb.+不定式”表示“某人(做某事)怎么样”。

通常表示根据事实判断人的品行，特征。

如：“聪明，愚笨，明智，错误等”。

注意：这一句型中常用描述不定式的逻辑主语的性格、品质的形容词，如good(好的)，kind(友善的)，nice(友好的)，polite(有礼貌的)，clever(聪明的)，foolish(愚蠢的)，lazy(懒惰的)，careful(细心的)，careless(粗心的)，wise(明智的)，right(正确的)，wrong(错误的)等。

3.It＋be＋名词＋不定式用于此句型的名词有：pity, shame, pleasure, one’s duty, one’s job, fun, joy, good manners, bad manners等。

例如：It's our duty to take good care of the old.What a pity it is for you to have missed such a wonderful film.It is good manners for the young to give their seats to the old.It's a shame for you to do such kind of thing.4. It takes sb.＋some time＋to do sth. 该句型意为“做某事花费某人多长时间”。

例如：It took us half an hour to ride to the town by bike.二、作表语主语和表语同为不定式时，通常主语表示条件，表语表示结果。

如：To see is to believe.动词不定式作表语常用于以下结构：My wish/ job/ aim/ goal is+不定式以及The next step/ /important thing/problem/measure is +不定式等。

例如：My wish is to be a teacher.My goal is to pass the college entrance examination(高考，大学入学考试).The problem is how to get there.The important thing in life is to have a great aim.(目标)Your job is to type the papers in the office.The next measure is to stop the river from being polluted.☆另外：A)当主语是一个由what引导的从句时，用作表语的不定式通常是说明what的具体内容的。

如：What I want is to go to the park tomorrow.B)不定式作表语常常用来表示预定要发生的动作，或表示未来的可能性或假设。

如：His greatest wish is to see an end to the war.All you have to do is (to) finish the job as quickly as possibly.All I can do is just smile at him and say nothing.注意：当主语中含有实义动词do的各种形式时，作表语的不定式通常省略“to”.三、作宾语许多动词都可和不定式搭配，即这些动词的用法决定了其后接带to的不定式作宾语。

有些动词只能接“疑问词+不定式”作宾语。

而句中的主语常常就是作宾语的不定式的逻辑主语。

常见的只能使用动词不定式作宾语的动词有：agree, choose, decide, hope, fail, wish, refuse, expect, manage, plan, intend, pretend, promise, offer, afford, demand, arrange等。

而常常接“疑问词+不定式”作宾语的动词有：decide,discover,forget,inquire（询问），know,learn,remember,see,settle,think,wonder.例如：They decided to build a highway between these two cities.She offered to help me when I was in trouble.He promised not to tell anyone about it.I don't decide/know what to do/where to go.I can't remember what to do.I forgot how to operate the machine.注意：当作宾语的不定式是较长的短语，常常用it作形式宾语，而把真正的不定式放到句末去。

常常这样用的动词有believe, think, consider, find,feel, make等动词。

可构成句型“动词+ it +adj. / n+to do sth.”句型，其中使用it作形式宾语，而将真正的宾语动词不定式置于句末。

例如：I think it necessary for us to have a good rest after the long work.She felt it her duty to help the old woman.I find it difficult to understand him.※四、作介词宾语动词不定式通常不能用作介词的宾语，但以下两点除外。

1）介词之后可以用“疑问词+不定式”作宾语。

如：He gave me some advice on how to write a good composition(作文).He talked with me about how to spend the frigid(极寒冷的) winter.2)以下介词之后常常用不带to的不定式作宾语，特别是当句中的谓语动词为实义动词do的各种形式时，尤其如此。

而谓语动词为其他动词时，也可用带to的不定式。

如：I have done nothing except eat and sleep this week.I couldn't do anything but wait here.The enemy(敌人)had no other choice but/than to surrender(投降).敌人除了投降之外，别无选择。

It had no effort except to make him angry.除了让他生气外，这起不了任何作用。

在下列短语后，but之后只能跟不带to的不定式。

如：His father could do nothing but wait for the doctor to arrive.We would do anything but confess(承认)our guilty.我们决不承认有罪。

She couldn't help but laugh at his clothes.她情不自禁地大笑他的着装。

I cannot but admire(钦佩) his courage.I could not choose but love her.我不禁爱上了她。

作宾补不定式作宾补时，其逻辑主语常常就是它前面的宾语。

1)可后接动词不定式作宾补的动词有：advise, allow, ask, beg, cause, challenge(挑战), convince(使信服), dare, drive(驱使), encourage, expect, forbid, force(强迫), hire, instruct(指导), invite, need, order, permit(允许), persuade, require, teach, tell, urge, hear, order, see, want, wish, worn(警告)等。

例如：The doctor advised her not to eat too much sugar.I wish you to go to the meeting with me.I persuaded him to give up smoking.She asked me to stay here.2)注意：有一类表示见解，看法的动词，如：believe, consider, count, declare, deny, feel, find, guess, imagine, judge, know, prove, realize, suppose, think等动词后常常接to be型不定式作宾补。