系表结构就是说明物质的一个性质，而不是一个动作之类，就是 I am ，he is，之类。is are am 都是系动词，不是动词。
系动词，亦称连系动词。作为系动词，它本身有词义，但不能单独用作谓语，后边必须跟表语，亦称补语（形容词），构成系表结构说明主语的状况、性质、特征等情况。
表语就是起表述作用的句子成分。它修饰的是主语。表语是用来说明主语的身份、性质、品性、特征和状态的。表语须和连系动词一起构成句子的复合谓语。
1 定义
系表结构有两部分构成：连系动词和表语。下面分别解释一下：
一连系动词：
连系动词分为三类：be 动词，感官动词，趋势动词。
1) Be 动词：am, is, are, was,were
2) 感官动词：sound, look, taste, feel, smell
3) 趋势动词：appear, become, grow, get, turn, seem, remain
2 内容
注意：
有一些动词既可以做连系动词又可以作及物动词和不及物动词。
He is growing very fast. ---不及物动词
I am growing apples in my backyard.---及物动词The sea is growing rough.---连系动词
He is tasting the food.--- 及物动词
The food tastes good.--- 连系动词
二表语：
下列成分都可以做表语：名词， 形容词，副词， 动词不定式，动名词，现在分词，过去分词，表语从句．
使用举例(注意：连系动词不能够单独作谓语，他们必须和表语一起工作构成谓语):
1) 名词:
False： I am.
Right： I am a student.
2) 形容词：
False： He became. Right： He became strong.
3) 副词：
False： She remained.
Right： She remained there.
4) 现在分词：
False： The story seemed.
Right: The story seemed interesting.
5) 过去分词：
False： The windows seemed.
Right: The windows seemed broken.
6) 动名词：
False： His job is teach English.
Right: His job is teaching English.
7) 动词不定式：
False： Her plan is become the winner in the game.
Right: Her plan is to become the winner in the game.
6）和7）的区别：
6）中动名词表示某人经常干某事：她从星期一到星期五天天教英语；
7）中动词不定式表示某人将要干某事：她的计划是将要成为比赛的胜者。
8) 表语从句：
False：The question is.
Right: The question is whether he will come here in time tomorrow.
Right: The question is what he is going to do next.
Right: The question is how he has managed to solve the problem by himself
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