导读：动词不定式是动词的一种非谓语形式，在句中不能单独作谓语。动词不定式具有动词的性质，它可以有自己的宾语和状语，从而构成动词不定式短语。它还可以有形式的变化，即一般式、进行式、完成式和被动式。同时，动词不定式也具有非动词的性质，相当于一个名词、形容词或副词，可以在句中担任主语、宾语、宾语补足语、表语、定语和状语。下面和长沙新东方的小编一起来复习一下。
动词不定式的几种常见结构
A.不定式的复合结构
动词不定式的逻辑主语(即不定式动作的执行者)通常是句子的主语或宾语。如果不定式的逻辑主语不是句子的主语，此时一般用"for
+名词(代词)+不定式"来构成不定式的复合结构，这种复合结构在句中可以做主语、宾语、表语、状语、定语。
This box is too heavy for the little boy to carry. 这个箱子让这个小男孩来搬太重了。
That's for you to decide.那个由你来决定。
He stood aside for me to pass.他站到一边让我通过。
I have some books for you to read.我有几本书送给你读。
B.be +不定式结构
"be +不定式"结构可以表示将来发生的动作，常有以下两种情况：
1.表示命令和指示
The room is to be locked.这房间要上锁。
You are not to stand here.你不能站在这里。
2.表示计划或安排
We are to begin the work next month.我们安排下一个月开始这项工作。
What's to be done next下一步该怎么办?
C.疑问词+不定式结构
疑问词who, what, which, when, where, how,
why后加动词不定式构成不定式短语，它在句中可作主语、宾语和表语。
I don't know whether to go to the meeting or not.我不知道要不要去开会。
The problem was how to get rid of the waste thrown by the
passengers.问题是如何处理乘客们丢弃的垃圾。
When to visit the Palace Museum has not been decided
yet.何时参观故宫博物院还没有决定。
D.withwithout +名词+不定式结构
"withwithout +名词+不定式"结构在句子中通常起状语的作用。
With so much work to do, I shall not be able to go to the cinema with
you.有这么多工作要做，我不能和你去看电影了。
With him to stay in the house, I feel quite safe.有他住在家里，我感到十分安全。
Without anything to eat, he died of hunger.由于没有东西吃，他饿死了。
E.It is +形容词+ forof sb + to do结构
在"It is +形容词+ of sb +不定式"结构中，形容词往往表示人物的性格和特征，如kind, silly, good, unwise,
clever, wrong, right, foolish, stupid, careless, rude, impolite, bold,
thoughtful, honest, bad, sensible, naughty等。在"It is +形容词+for sb
+不定式"结构中，形容词通常表示事物的性质，如important, possible, impossible, necessary, difficult,
hard, reasonable等。
It's kind of you to think so much of us. 难为你这么为我们着想。(= You are kind to
think so much of us.)
How careless it is of him to break such a valuable
vase!他真不小心，把如此贵重的花瓶打破了。
It is easy for me to see through his trick.我很容易看穿他的鬼把戏。(=For me to see
through his trick is easy.)
It is hard for him to get rid of his bad habits.他很难改掉自己的坏习惯。
比较：
It is good lf you to help me with my English. 你真好，帮助我学英语。(强调you的特征=You are
good to help me.)
It is good for you to give up smoking. 戒烟对你有好处。(强调的是give up smoking这一行为=Fof
you to give up smoking is good.)
F.分裂不定式
动词不定式to do通常是不拆开的，但偶尔也可在不定式符号to和动词原形之间插入一个副词，构成分裂不定式。
He was too ill to completely carry out that program.他病得太重，不能完成那个项目。
He has made up his mind to once more try this method. 他已经下定决心再试试这个方法。
G.用作独立成分的不定式
有一些不定式短语可以作状语修饰整个句子，也可被称为插入语。
To be honest, we are not sure to find the girl in the
forest.说老实话，我们不能确保在森林里能找到那个女孩。
To be frank, I don't agree with what you said. 坦率地说，我不同意你说的话。
必背：用作独立成分的不定式
to tell you the truth说老实话
to be frank 坦率地说
to begin with首先
to be brief简言之
to make a long story short长话短说
to be exact精确地说
to say nothing of姑且不说
to conclude总而言之
to be sure诚然，固然
to do him justice说句对他公道的话
so to speak可以这么说
H.用主动式表示被动含义的不定式
动词不定式在句中究竟用主动还是被动，有时比较复杂，主要有下面几种情况：
1.不定式做后置定语，和被修饰的名词或代词构成逻辑上的动宾关系，但又和该句主语构成逻辑上的主谓关系时。
Do you have anything to say on this question针对这个问题你有什么要说的吗?
He is a pleasant person to work with.他是一个与其合作起来令人感到愉快的人。
2.不定式作形容词的宾语，和句子主语构成逻辑上的动宾关系时。
The book is difficult to understand.这本书很难理解。
The chair is comfortable to sit on.这把椅子坐起来很舒服。
3.There be结构中，当说话人考虑必须有人去完成某件事时。
There is nothing to worry about.没什么可担心的。
There is nothing to fear.没有什么可害怕的。
比较：
There is a lot of work to do.有许多事情要做。(表示某人必须做这工作)
There is a lot of work to be done.有许多事情要做。(强调有许多事情必须做)
She has two letters to type.她有两封信要打。(自己打)
She has two letters to be typed.她有两封信要打。(别人打)
I.表示虚拟语气的不定式完成式。
I hoped to have met him at the railway station, but he didn't turn
up.我本希望在火车站接到他，但他未露面。
We would love to have gone to the match, but the tickets were all sold
out.我们原想去看这场比赛的，但票已售完了。
The plane was to have taken off at 9, but something went
wrong.飞机原计划九点起飞，但出现了一些故障。
J.用于感叹句。
不定式可用于感叹句，含有惊异、不满、惋惜或赞美等感情色彩。
To think that he should do this!想想，他竟然干出这等事!(表示惊讶)
Oh, God, to see her dance !哦，天哪，看看她的舞蹈!(表示赞美)
To think that all the money has been wasted.想想，所有的钱都被浪费掉了!(表示不满)
(来源：新东方在线高考辅导)
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