一、A=B。即A与B双方程度相等时，用“as+原级+as”的结构来表示。例如：
Oil produced waste gases almost as harmful as the gases from factories.
Tom runs as fast as Jack.
He is a fellow as tall as his elder brother.（=He is as tall a fellow as his elder brother.）
二、A≠B。即A与B双方程度不等时，则用“not as(so) +原级+as”的结构来表示。例如：
London is not so modern as New York.
Sound does not travel as fast as light.
No one is so blind as the people who will not see.
三、A=nB。 即双方相比，A是B的若干倍时，用“倍数+as+原级+as”的结构来表示。例如：
This room is about two-thirds as large as that one.（=This room is about two-thirds the size of that one.）
There are twice as many students in our school as there were in 1949.
四、A>B。 即A方超过B方时，要用“比较级+than”的结构来表示。例如：
She is five years older than I. （= She is older than me by 5 years.）
He studies harder than any of the others in his class.
五、AThis lesson is less difficult than that one.
It rains less often in spring than in summer.
He is less of a fool than I thought he was.
六、 A>n+B。 即A方超过B方的程度和数量时，用“much (far)/ three times/ five years etc.+比较级+than”的结构来表示。例如：
He works far better than you.
Ann is much nicer than her sister.