补语
补语的作用对象是主语和宾语,具有鲜明的定语性描写或限制性功能,在句法上是不可或缺的。补语是起补充说明作用的成份。最常见的是宾语补足语。名词、动名词、形容词、副词、不定式、现在分词、过去分词都可以在句子中作宾补。

主语补足语
它用在系动词后，是句子的一个基本成分。常用主－系－表结构。
1.. -- Who broke the vase? --谁打碎了花瓶？
-- Me. --我。 （me做主语补语= It's me.）

2.John hoped the passenger would be Mary and indeed it was her. （her做主语补语） 约翰希望那位乘客是玛丽，还真是她。

宾语补足语
1.不定式(to do)
Father will not allow us to play on the street. 父亲不让我们在街上玩耍。
We believe him to be guilty. 我们相信他是有罪的。
We made him copy the sentence.
He is made to copy the sentence.
I felt my hands tremble.

2.名词
At the meeting we elected him monitor.
I think your brother a clever boy.

3.形容词
What you said made Xiao Wang angry.
I found the classroom empty.

4.副词
Please call the students back at once.
He was seen to take his cap off.

5.现在分词
We hear him singing in the hall.
I found him lying in bed, sleeping.

6.过去分词
He saw his face reflected in the water.
I heard it spoken of in the next room.

主语补足语与宾语补足语的联系
1、主动语态中的宾语补足语，可以转化为被动语态中的主语补足语。
They caught the boy stealing. （stealing 作为宾语补足语） 转化为被动语态 The boy was caught stealing. （stealing转化为主语补足语）

2、被动语态的主语补足语与主动语态的宾语补足语是密切相关的。
(1) I saw him playing basketball yesterday.
(2) He was seen playing basketball yesterday.
句（1）中的含义不是我看见他，而是我看见他正在打篮球。playing basketball是宾语him的补足语。所以叫宾语补足语。
句（2）中的含义也不是他被看，而是别人看见他正在打篮球。这里的playing basketball是主语he的补足语，故称作主语补足语。主语和主语补足语一起称作复合主语。所以含有主语补足语的句子一般是被动语态，谓语动词是可以接复合宾语（宾语+宾语补足语）的及物动词。句首的主语就是主语补足语的逻辑主语。