“as...as” 是一个常用的英语比较结构。
一、基本用法
用于比较两个人或事物在某方面的程度相同。基本结构是 “as + 形容词 / 副词原级 + as”。
例如：“This book is as interesting as that one.”（这本书和那本书一样有趣。）这里是比较两本书在 “有趣” 这个特征上程度相同，“interesting” 是形容词原级。
再如：“He runs as fast as his brother.”（他和他哥哥跑得一样快。）此句中比较两人跑步的速度，“fast” 是副词原级。
否定形式为 “not as/so + 形容词 / 副词原级 + as”，表示 “不如……”。
例如：“This room is not as large as that one.”（这个房间不如那个房间大。）
又如：“She doesn't sing as well as her sister.”（她唱歌不如她姐姐唱得好。）
二、变体及特殊用法
“as...as possible” 表示 “尽可能……”。
例如：“Please come as early as possible.”（请尽可能早来。）
“You should do your homework as carefully as possible.”（你应该尽可能认真地做你的家庭作业。）
“as much/many as...”
“as much as + 不可数名词” 表示 “和…… 一样多的（不可数名词）”，例如：“He drinks as much water as his father every day.”（他每天和他父亲喝一样多的水。）
“as many as + 可数名词复数” 表示 “和…… 一样多的（可数名词）”，例如：“There are as many students in this class as in that class.”（这个班和那个班的学生一样多。）
“as...as one can” 与 “as...as possible” 意思相近，也是 “尽可能……” 的意思。
例如：“You should read as many books as you can.”（你应该尽可能多地读书。）