非谓语动词

　　不定式

　　形式

　　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

　　完成式: 不定式的一般形式所表示的动作, 通常与主要谓语表示的动作(状态)同时(或几乎同时)发生, 或是在它之后发生. 假如不定式所表示的动作, 在谓语所表示的动作(状态)之前发生, 就要用不定式的完成式。

　　I am glad to have seen your mother (= I am glad I have seen your mother).

　　(比较: I am glad to see you.)

　　He is said to have written a new book about workers.

　　He pretended not to have seen me.

　　进行式: 如果主要谓语表示的动作(状态)发生时, 不定式表示的动作正在进行, 这时要用不定式的进行式。

　　You are not supposed to be working. You haven't quite recovered yet.

　　We didn't expect you to be waiting for us here.

　　He pretended to be listening attentively.

　　完成进行式: 在谓语所表示的时间之前一直进行的动作, 就要用不定式的完成进行式.

　　The struggle was known to have been going for twenty years.

　　We are happy to have been working with you.