比较级的基本结构如下：
一、由than构成的比较级：
A+is/are+形容词的比较级+than+B.
A+行为动词＋副词的比较级+than+B.
e.g.The book is cheaper than that one.
l run faster than his brother.
二、由as...as构成的平行比较级：
11A is/are as+形容词+as.（肯定形式）
A+行为动词+as+副词+as.（肯定形式）
e.gWe are as careful as they.
we write as carefully as them.
2、A is/are not as/so+形容词+as.（否定形式）
A+助动词+not+行为动词原型+as+副词+as.（否定形式）
e.g.The boy isn't as tall as his sister.=The boy is shorter than hissister.这个男孩没有他姐姐高。
He doesn't sing as well as his sister.=He sings worse than his sister.
We aren't as careful as they.=We are less careful than they.
三、由more，fewer，less+名词构成的比较级：
1、more“比.......多”，后接复数名词或不可数名词
l have more news books than my cousin.
He has more milk than I.
2、less“比.....少”，后接不可数名词
He has less water than me.
3、fewer“比....…少”，后接复数名词
They have fewer flowers than we.