不定式的用法

　　动词不定式具有名词、形容词和副词的特征。因此在句中可以做主语、表语、宾语、宾语补足语、定语和状语。

　　一、不定式做主语:

　　1、不定式做主语一般表示具体的某次动作。===动名词doing表示习惯的,经常的动作。

　　e.g:To finish the building in a month is difficult.

　　To do such things is foolish.

　　To see is to believe.(对等)

　　注:1).不定式作主语时,谓语用单数

　　2).当主语较长,谓语较短时,常用it做形式主语,而将不定式放到谓语的后面。

　　it做形式主语,不定式放在谓语动词之后常用于下列结构中:

　　(1)Itis/was+adj.+ofsb.todo…

　　(2)Itis+adj.+forsb.+todo…

　　It is easy/difficult/hard/foolish/unwise/right/wrong/unnecessary

　　(3)itis+a+名词+todo...

　　It is a pity/a pleasure/a pleasant thing/one’s duty/an honor/a shame/a crime/no easy job…todo

　　It takes (sb.) sometime/courage/patience…to do…

　　It requires courage/patience/hardwork…to do…

　　*注意:probable和possible均可作表语,但possible可以用不定式作真实主语,而probable不能用不定式作真实主语。

　　It is probable for him to come to the meeting. (错)

　　It is possible for him to come to the meeting.

　　It is possible/probable that he will come to the meeting.

　　二、不定式做表语

　　主语是以aim duty hope idea intention plan job suggestion wish purpose task等为中心词的名词词组或以what引导的名词性从句表示,后面的不定式说明其内容,不定式作表语常表示将来或现在的动作或状态。

　　eg: My idea is to climb the mountain from the north.

　　Your mistake was not to write that letter.

　　What I would suggest is to start work at once.

　　三、动词不定式作宾语

　　以不定式结构为宾语的动词有:

ask, agree, care, choose, demand, decide, expect, fail, help, hope, learn, manage, offer, plan, prepare, pretend, promise, refuse, want, wish等只能用动词不定式作宾语

　　口诀(接不定式作宾语的动词)

　　想要学习早打算(want learn plan)

　　快准备有希望(prepare hope wish expect)

　　同意否供选择(agree offer choose)

　　决定了已答应(decide be determined promise)

　　尽力去着手做(manage undertake)

　　别拒绝别假装(refuse pretend)

　　失败不是属于你(fail)

　　E.g.Tom refused to lend me his pen.

　　We hope to get there before dark.

　　The girl decided to do it herself.

　　*注意:某些及物动词可用-ing也可用动词不定式作宾语但意义不同的有

　　Stop go on remember forget

　　Regret try mean can’t help

　　Be used to

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