as soon as （= 一···就···）,引导时间状语从句,如 I recognised him as soon as I saw an old friend of mine (= 我一看到我的一个老朋友,就人出他来了)
as + adj./ adv.+ as (= 和 ··· 一样),引导比较状语,如 The boy is as tall as his father (= 男孩已经和他的爸爸一样高了 ) ；He plays basketball as well as Tom (= 他篮球打得和汤姆一样好)；
not as + adj / adv + as (= 和···一样不),也也引导比较状语,但表示否定,如 The boy is not as tall as his father (= 男孩没有他爸爸高)；He does not play basketball as well as Tom (= 他篮球打得没有汤姆好)；
as ...as possible (= 尽可能地···),通常做状语,如 Please write to him as soon as possible (= 尽快地给他写信)；The thief ran as fast as possible = The thief ran as fast as he could (= 小偷尽快地跑了).