语法之于英语四级考试准备的重要性实际上并没有降低，在语言知识运用、作文、阅读长难句分析方面起到的作用是不可替代的。下面是2014年英语四级常用语法(4)，介绍非谓语动词。
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