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,go
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 window seemed.
Right： The window 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.