外研2003课标版《Grammar》精品PPT课件优质课下载

外研2003课标版《Grammar》精品PPT课件优质课下载

3. To open a book is always beneficial.

4. Never too old to learn, never too late to turn.

语态

时态

主动

被动

一般式

to do

to be done

进行式

to be doing

完成式

to have done

to have been done

否定式：not + to do/ to be done/...

﹨

不定式的一般式所表示的动作,通常与谓语的动作(或状态)同时(或几乎同时)发生,或在它之后发生。

I saw him go out.

We plan to pay a visit.

When do the actions of the verbs take place?

如果谓语的动作发生时, 不定式表示的动作正在发生, 不定式用进行式。

It is frightening to be cycling to work in a sandstorm.

不定式的动作在谓语动作之前发生,不定式用完成时。

I’m sorry to have kept you waiting so long.

不定式作主语往往放在谓语动词之后, 用it作形式主语, 为了避免句子头重脚轻。