动词不定式有主动语态和被动语态 在句子中作主语 表语和宾语等
动词不定式有主动语态和被动语态。
一 动词不定式的主动语态有5种形式
一般式 to do (to do sth是动词不定式短语）
进行式to be doing
完成式 to have done(done代表过去分词 ）
完成进行式to be doing
动词不定式的被动语态有2种形式
一般式 to be done
完成式 to have been done
否定式 not +to do
动词不定式用法
二 动词不定式用法：在句子中充当主语，宾语，定语，宾语补足语等句子成分，及其他用法。
1动词不定式（短语）作主语
To rebuild the factory will take them 3 years.
他们要重修这个工厂得3年。
常用it作形式主语，动词不定式（短语）作真实主语。
It is difficult to imagine the modern world without oil.
很难想象没有油的现代世界。
疑问词+动词不定式（短语）作主语
When to start remains undecided.出发时间还未定。
其他句式：It seems/appears adj to do sth
It seems impossible to save money.攒钱是不可能的。
It be动词 adj for/of sb to do sth
It was silly of us to believe him.我们真傻居然相信他们。
It be动词 + sb some time to do sth
It’s our duty to take care of the old.
照顾老人是我们的责任。
2 动词不定式作表语
His dream is to be a businessman.
他的梦想是成为一名商人。
The question is how to get there.
问题是怎样到达那里。（疑问词+动词不定式）
注意：有时可以省略to
The only thing I can do now is (to) go on by myself.
我现在唯一能做的就是自己继续进行下去。
What I want to say is (to) be yourself . 我想说的就是做你自己。
3 动词不定式作宾语
及物动词（vt) +动词不定式,这类动词有:afford, want, wish, learn, like ,forget, hope, intend, determine,expect, fail, begin, attempt， care to do sth愿意/喜欢做某事, claim声称, continue,choose, agree, decline, desire, determine, try,undertake, manage设法， mean, refuse, promise, remember, require, offer主动提出，seek, start，ask, arrange安排，pretend假装，beg恳求等。
有时可用it作形式宾语，动词不定式作真正宾语。这些动词常有：believe,consider,think, feel, find, imagine, know, make, prove, realize,show, suppose, think, understand等。
We think it very important for us to learn a foreign language well.
我想对我们来说学好一门外语是很重要的。
疑问词+动词不定式也可作宾语
I don’t decide where to live.我没有决定住哪里。
where作副词，所以live后面不加介词in.
I don’t decide which room to live in.
我没有决定住哪个房间。
I don’t know what to do. 我不知道做什么。
I don’t know how to do it. 我不知道怎么做。
4 动词不定式作定语
His book to be published next month is based on a true story.
他下个月将被出版的书是以真实的故事为基础的。
to be published next month作定语，修饰book
My wish to visit France has come true at last.
我想去法国旅游的愿望终于实现了。
I borrowed some books to read during the holiday.
我借了一些假期要读的书。to read这个动作发生在借之后。
They have a big house to live in.他们有大房子住。
介词in不能省略。
当前面名词是time，place或way时，不定式后面的介词习惯省去。
He had no place to go.他没有地方去。
They had no place to live.他们没有地方住。
Mice ran out of the fields looking for places to hide.
老鼠从地里跑出去找地方躲藏。
注意：I have something to send.= I have something to be sent.
我有些东西要寄。
5动词不定式作状语
目的状语 He ran so fast as to catch the first bus.他跑得这么快为了赶上头班车。
结果状语 He searched the room only to find nothing.
他找遍了这个房间结果却一无所获。
原因状语 I’m glad to see you. 见到你我很高兴。
I’m very happy to have passed the exam. 我很高兴已经通过了考试。
评注性状语To be honest, I don’t like western food.
6 动词不定式作补语
在ask, want, encourage, wish, advise,forbid, allow, expect, find, get, invite, tell,remind, consider等动词后可以跟动词不定式作宾语补足语。
We saw them enter the house. 我看到他们进入房间。宾语补足语
They were seen to enter the house. 他们被看到进入房间。to enter the house 作主语补足语。
My father doesn’t allow us to play on the street.我爸爸不让我们在街上玩。
在感官动词后，如feel, see,hear, watch, look at, listen,notice, observe,在使役动词，如let, make, have后，不定式省略to.
He noticed someone leave the room.他注意到了有人离开房间。
变成被动后，要加上to. They were made to retell the text by the teacher.老师要他们复述课文。
People found that they have moved out.
=They were found to have moved out.他们被发现已经搬走了。
to have moved out作主语补足语。
It is said that they have developed a new technique.
= They are said to have developed a new technique.
据说人们已经发研发了一项新技术。
to have developed a new technique作主语补足语。
7 动词不定式构成词组
be free to do something 有空做某事
be afraid to do something 害怕作某事
be careful to do something 认真做某事
too...to 太... 而不能...
The hat is too large to wear. 这帽子太大，没法戴。
8 动词不定式主动形式表被动意义
The book is difficult to understand. 这本书很难理解。
We must know what to say at the meeting.
我们必须知道会上说什么。
It is impossible to finish. 不可能完成。
The house is to let.此房出租。
She was to blame for the accident.她应该为这次交通事故负责。