l)构成：形容词，副词的原级形式是形容词
2)用法：表示双方在程度，性质，特征等某方面相等时，用" as 十原级形容词或副词十 as"的结构；
表示双方不相等时，用" not so (as)十原级形容词或副词十 as"的结构；
表示一方是另一方的若干倍时，用"倍数十 as十原级形容词或副词十 as"的结构．
e.g. Ms．Sun speaks English as fluently as you．
This building looks not so (as) high as that one．
This room is three times as large as that one.
