动词不定式
动词不定式（infinitive）由 to（to 不是介词，只是一个标记）引导动词原形。本质上讲，动词不定式才表示一个“动作”，动词原形只是一个词形。动词不定式或动词不定式短语（infinitive phrase）可以在句中充当名词，形容词，或副词成分。
充当名词
作主语
To be or not to be, that is the question.
To know her is to love her.
与 it 连用作逻辑主语
It is good of you to talk to me.
作宾语
He likes to hunt.
作表语
They are to get married soon.
充当形容词
作后置定语
I would like a sandwich to eat.
I don’t have anything to wear.
充当副词
作目的状语
She came to collect her pay cheque.
作原因状语修饰形容词
I am happy to be here.
The dog is naughty to destroy our couch.
与 too 连用构成 too … to …，作程度状语修饰形容词
There’s too much sugar to put in this bowl.
I had too many books to carry.
一些需要带动词不定式的动词
| agree | demand | long | pretend |
| aim | fail | love | promise |
| arrange | forget | manage | propose |
| ask | hate | mean | refuse |
| begin | help | need | remember |
| choose | hope | offer | try |
| claim | intend | plan | want |
| continue | learn | prefer | wish |
| decide | like | prepare |
不带 to 的动词不定式
动词不定式有时不带 to（称为 bare infinitive），具体情况比较复杂，通常来说：
1. 情态动词 can, could, may, might, must, shall, should, will, would, need not, dare not 之后不带to；
I can’t agree with you on this, though I would like to be able to help you.
You must finish your own work before you go out, but you don’t have to help your sister.
It will be hot and sunny today so you should put on plenty of sunscreen and you ought to wear a hat.
He needn’t take time off work, but he needs to rest in the evenings and get a good night’s sleep before he sets off on the new expedition.
2. 感官动词如 feel, see, hear, watch, notice 的宾语之后不带 to；
I saw him pour the medicine down the loo and I heard him laugh to himself.
3. why/why not 之后不带 to；
Why wait? Let’s leave now.
4. would rather, had better 之后不带 to；
I’d rather swim in the pool than go down to the beach.
Geoffrey has just driven up in his car. You’d better see what he wants.
5. 使役动词 let, make, have 的宾语之后不带 to；
I cannot make you take this medication, I can only ask you to take it.
I can’t let you go to bed hungry. You must let me prepare you some supper.
If you wait, I’ll have someone collect it for you.
6. help 的宾语之后可带可不带 to；
Could you help me (to) look for my car keys? I can’t find them anywhere.
7. bid 的宾语之后可带可不带 to；
He bade (= asked) them (to) leave at once.
8. what … do 的 be 动词之后可带可不带 to；
I hate shopping so what I’ve done is (to) order a new computer over the Internet.
All I did was (to) suggest that she should lend him no more money. I didn’t insist on it.
9. do/do not 之后不带 to；
I do/don’t like dancing.
10. 连词，如 and, or, but, except, than, rather than, as 前面有动作时，连词之后的动词可省略 to；
I would like you to tidy the house and (to) wash the dishes before I get home.
Would you prefer to have a snack now or (to) wait until later before we eat?
I could find nothing to do this afternoon, except read my book.
My son does nothing but watch TV when he gets home from school.
It’s quicker to bike to the station rather than take the car.
I have to fix breakfast for everybody as well as take the children to school before I can leave for work.
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