动词不定式 (回顾&拔高)

不定式有一般式.进行式.完成式和完成进行式；有主动式，也有被动式。以动词do为例

	主动形式	被动形式
一般式	to do	to be done
完成式	to have done	to have been done
进行式	to be doing	------------
完成进行式	to have been doing	--------------

1.不定式的否定形式

否定式的否定形式是在不定式符号to前加not 构成：He decided not to go home.

2.疑问词+不定式结构

疑问词who, which, what, when, where, how, whether等后接不定式,构成不定式短语,在句中作主语.表语.宾语等。 When to start has not been decided.（主语）

I don’t know what to choose.（宾语）

The question is how to put the plan into practice.（表语）

3.动词不定式的时态的用法

（1）一般式：不定式的一般式所表示的动作与谓语动词动作同时发生或发生在谓语动词动作之后，

I'm glad to meet you.

（2）进行式：不定式的进行式所表示的动作与谓语动词动作同时发生，例如：

The boy pretended to be working hard.

（3）完成式：不定式的完成式表示的动作发生在谓语动词动作之前，例如：

I happened to have seen the film.

4.动词不定式的语态的用法

当不定式的逻辑主语是不定式所表示的动作的承受者时,不定式一般要用被动语态

The books and magazines are not allowed to be taken out of the reading room.

如果不定式表示的是一个比谓语动作发生得更早的动作,这时不定式可用完成式的被动式

The novel is said to have been translated into seven languages.

5.动词不定式省略to的情况

1） 在助动词或情态动词后面: May I ask you a question? 我可以问你一个问题吗?

2) 在 make, let, see, watch, hear, notice, feel, have, listen to , look at等动词后(作宾语补足语)

Let me hear you play the piano. 让我听你演奏钢琴吧。

3) 在why引起的某些问句中: Why turn off the gas? 为什么不再试一下？

4) 在had better, would rather, would rather…than, would sooner, would sooner…than, cannot but, do nothing but 等结构后面

He would rather /sooner die than surrender(他宁死不屈)

My mother could do nothing but wait for the doctor to arrive (我妈妈没办法,只好等医生来)

5) 在 “Why…” 或 “Why not…” 一类表示建议的句型中

Why not join us? (= Why won’t you join us?) 为什么不加入到我们中来吗?

6)在介词except, but之后,如果其前有动词do的某种形式,不定式一般不带to,反之则带to

There is nothing to do except wait till it stops raining (没办法,只好等雨停了)

There is no choice but to wait till it stops raining (没办法,只好等雨停了)

7)当作宾语的不定式再次出现时,为了避免重复,不定式往往省略,只保留不定式符号to.常出现在下列动词后:want, wish, like, love, hope, plan, try ,hate 等

You don’t have to eat if you don’t want to.如果你不想吃,就不必吃了