1)主语
是句子的主体，动作的执行者，它可以是名词、代词、动名词、动词不定式，甚至句子也可以担当主语。例如：
The apple is red. (the apple：名词作主语)
He likes apples. (he：代词作主语)
Reading in bed is a bad habit. (reading：动名词作主语)
To say is easier than to do. (to say：动词不定式作主语)
What he did makes the teacher very angry. (what he did：句子作主语)
2)谓语
通常由单动词或动词短语构成，说明或描述主语的动作、状态或特征。例如：
My mother enjoys shopping. (enjoy：单动词作谓语)
The boys often play football on the playground. (play football：动词短语作谓语)
