动词不定式基本形式为： to+动词原形，就是老师经常说的 to do有些动词不定式不带to否定形式为：not (to)+动词原形
一提到动词不定式，很多同学只知道表目的，其实它的用法还有很多！
多数情况用it作形式主语，把真正的主语——动词不定式置于句末，特别是不定式短语较长时。
动词不定式作主语，谓语动词用第三人称单数形式。如：
For him, to talk with his mother is necessary.
=It is necessary for him to talk with his mother.
动词不定式做表语，常说明主语的内容、性质、特征。常可转换成主语。如：
The best way to improve your English is to join an English club.
=To join an English club is the best way to improve your English.
★可以接带to的动词不定式作宾语的动词主要有：
要求选择同意(ask, choose, agree)，
期望决定学习(expect, hope, decide, learn)，
宁可拒绝假装知道(prefer, refuse, pretend, know)，
希望想要愿意(wish, want/need, would like / love)等。
如：
We decided to talk to some students.
He prefers to eat white bread and rice.
★动词decide, know, learn, show, teach, tell...后可用“疑问词+to的不定式短语”作宾语，但why后面的不定式不带to。如：
Could you please tell me where to park my car?
★动词feel, find, make, think等后面，可以用it作形式宾语代替真正的宾语—动词不定式，句子结构是sb. feel / find / make / ...+ it+adj. / n.+to do...。如：
I find it difficult to remember everything.
★既可接动词不定式又可接v-ing形式作宾语，意思差别不太大的动词有begin, start, like, love等。如：
Then I started to watch English-language TV.
I like to eat vegetables.
★后接动词不定式或v-ing形式作宾语，意思差别较大的动词有forget, remember等。
后接不定式作宾语，表动作尚未发生；后接ving形式作宾语，表动作已经发生。
stop to do停下来做另外一件事，stop doing停止做、不做当前这件事；
try to do尽力做，try doing试试看；
go on to do接着做另外的事，go on doing继续做原来的事。
When I left home, I had forgotten to bring it with me.
I stopped using them last year.
★句子的主语或宾语是动词不定式的逻辑主语，不定式与其所修饰的名词、代词等存在逻辑的动宾关系时，用动词不定式的主动式。
I have so much homework to do today.
It’s a good place to visit.
★作定语的不定式如果是不及物动词，且与所修饰的词之间有动宾关系，要在不定式后加适当的介词。
I need a room to live in.
★在主、被动语态句里用带to的动词不定式作补语的动词主要有：
要求允许提议(ask, allow, advise)，
期望邀请鼓励(expect, suppose, invite, encourage)，
教导告诉想要(teach, tell, want)，
等待希望愿意(wait for, wish, would like / love)。
She asked me not to speak Chinese in English class.
★下列动词，多数动词是感官动词和使役动词，当动词不定式作补语时，在主动语态句里不带to，被动语态句里要将省略的to补上。包括：
四“看”：look at, observe, see, watch，
三“让”：have, let, make，
二“听”：hear, listen to，
一“感觉”：feel，
一“注意”：notice。如：
This picture makes me feel tense！
I was made to say sorry to him.
★help后接动词不定式作补语，to可带可不带。如：
Using email English helps you write quickly.
★be said, be sure, happen, seem等后面可以接带to的动词不定式作主语的补语。如：
He doesn’t seem to have many friends.
Be sure not to miss them if they come to a city near you.
★目的状语，置于句首或句末，置于句首时常表示强调。如：
A group of young people came here to(in order to) discuss this question.
★原因状语，多见于“sb.+be+adj.+to do...”结构句中。如：
I’m sorry to trouble you. I’m glad to see you.
★结果状语，多见于“too...to”，“enough to...”结构句中。如：
Then I’m too tired to do well. What should I do?
The room needs to be big enough for three people to live in.
★独立动词不定式多用作插入语，表示说话人的心理状态或对事情的看法。如：
To be honest, I only eat food that tastes good.
To begin with, she spoke too quickly, and I couldn’t understand every word.
动词不定式的复合结构是“for / of sb. to do sth.”，for / of引出不定式动作的逻辑主语。这种结构在句子中可以作主语、宾语、表语、定语、状语等。
不定式复合结构作主语时，需注意：
It’s + 形容词 + for / of + sb + to do sth.
for前面的形容词是dangerous, difficult, easy, hard, heavy, important, interesting, necessary等，一般说明不定式动作的特性，不说明人的特性。
如：
It’s dangerous for children to swim in the river.
当上面的形容词指的是sb的性质时，用介词of。
这些形容词往往修饰人：careful, clever, foolish, good, kind, nice, wise,bad, polite, careless
It’s very nice of you to say so.
带疑问词的不定式短语动词不定式前面可以带疑问代词what, which, who或疑问副词how, when, where, why等。
这种结构起名词的作用，在句子里用作宾语、主语、表语等，或者单独使用。
I don’t know what to do next.
Where to go is not decided yet.
单独使用时相当于一个特殊疑问句,在复合句中则可变为一个从句。
What to do next? =What will we / you do next?
Can you tell me how to do that?=Can you tell me how I should do that?
动词不定式的否定式不定式的否定式是not to do...，不带to的不定式的否定式是not do...
Sometimes they decide not to talk to each other.
常见的与不定式连用的词组和句型Why not do…?=Why don’t you do …? had better (not) do …
would rather do … prefer to do rather than do
Could/Would/Will you please…? It takes sb +时间/金钱+ to do sth.
It’ s time to do… It’ s one’s turn to…
如： Why not take a holiday?
It takes me an hour to walk there.
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