否定式：not +不定式

　　不定式的时态

　　一般说来，不定式一般式表示的动作有时与限定动词表示的动作同时发生，也有时发生在限定动词表示的动作之后。如：

　　Who heard him say that?

　　He seems to know this.

　　I hope to see you again.

　　不定式进行式表示动作正在进行，通常与限定动词表示的动作同时发生，如：

　　They are said to be building another bridge across the river.

　　I happened to be going that way too.

　　不定式完成式表示的动作发生在限定动词表示的动作之前，如：

　　I am sorry to have given you so much trouble.

　　I am glad to have seen your mother.

　　不定式的句法功能

　　(1)作主语

　　To talk with him is a great pleasure.

　　不定式短语作主语时，为了保持句子的平衡，往往以it作形式主语，而把不定式短语置于谓语动词之后，如：

　　It’s nice to hear your voice.

　　(2)作表语

　　Her wish is to become an artist.

　　(3)作宾语

　　常用于及物动词: want , hope, wish, like, need, hate, offer, prefer, begin, start, attempt, decide, determine, expect, promise, pretend, refuse ,afford, manage, help等之后，如：

　　You should continue to learn as long as you live.

　　注1：如果作宾语的不定式又有自己的补语，则须用先行词it 作形式宾语，而将真正的宾语不定式后置，如：

　　They found it impossible to get everything ready in time.

　　注2：不定式一般不能作介词的宾语，只有在极少数介词如:but, except等后边才行。此时不定式可以带to或不带to,如：

　　In very cold winter weather a cold-blooded animal has no choice but to lie down and sleep.

　　There was nothing left to do but clean the windows.(前边有do, to 省略)

　　但“疑问词+不定式”结构可以作介词的宾语，如：

　　I have no idea about what to do next.