动词不定式的时态和语态
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.如果不定式所表示的动作与主要谓语动词所表示的动作同时(或几乎同时)发生或发生在主要谓语之后，通常用不定式的一般形式。如：
I saw him go out.
I‘m glad to see you.
2.如果不定式所表示的动作发生在主要谓语动词或特定的时间之前，不定式就要用完成式。如：
I intended to have telephoned you， but I forgot to.
I should like to have bought a dictionary.
3.不定式进行式表示主要谓语动词所表示的动作发生时，不定式所表示的动作正在发生。如：
I am glad to be talking with you. She pretended to be listening attentively.
4.不定式完成进行时表示的是一个开始于过去某一时刻但一直延续到谓语动词发生的那一时刻的动作。如：
He was thought to have been working on the project for two years.
5.不定式的被动语态
当不定式的逻辑主语是动作的承受者时，这个不定式要用被动式，包括它的各种时态在内。如：
She doesn‘t like to be treated as a guest.
她不喜欢被当作客人对待。
They want their TV set to be fixed right now.
他们想把电视机马上修好。
There are a lot of things to be done.
有许多事要做。
This is the text to be read next time.
下次就读这篇课文。
注意：有些习惯用法中，只能用主动语态。如：
The house is to let.
这房子要出租。
A lot of work still remains to do.
许多工作有待去做。
不带to 的不定式
1.表示感觉的动词see， hear， feel， notice， watch， observe和have， let， make后的宾语可接不带to的不定式。
He noticed the man enter the room.
他注意到有人进屋了。
They observed her do the experiment.
他们观察她做实验了。
2.help后的不定式可以带to也可以不带to.
Can you help me (to) clean up after the meal?
饭后你能帮我洗碗吗?
3.有些类似于情态动词的词语(如rather than， had better， would rather， might as well等)之后，不定式不带to.如：
We might as well go without him.
我们可以不让他跟去。
You‘d better go now.
你最好现在走。