之前小编与大家一起学习了形容词比较等级的构成方式，而形容词比较等级用于句子当中便形成了所谓的“比较结构”。英语比较结构最主要的有三种：as...as结构，more...than结构以及the most...结构。as...as结构意为“和...一样”，其用法主要如下：

　　一、基本模式：as+形容词原级+as-分句

　　1.主句主语与as-分句主语不同，比较项目相同，此时as-分句有所省略。如：

　　Jack is as clever as Tom.

　　2.主句主语与as-分句主语相同，但比较项目不同，此时as-分句不可用省略句。如：

　　The girl is as brilliant as she is beautiful. (这个女孩既漂亮又聪明。)

　　3.主句主语与as-分句主语不同，比较项目也不同，此时as-分句不可用省略句。如：

　　Her uncle was as base and unworthy as her father had been upright and honorable.

　　(她叔叔卑鄙龌龊，不像她父亲那样正直可敬。)

　　4.基本模式的否定形式：

　　Jack is not as clever as Tom. 或 Jack is less clever than Tom.

　　二、变体模式：

　　1. as many/much+名词+as-分句：

　　She has eaten as many apples as her sister.

　　He took as much water as he needed.

　　2. as+形容词原级+名词词组+as-分句：

　　Lucy is as clever a girl as her sister.

　　3. 变体模式的否定形式：

　　He didn’t take as much water as he needed.

　　需要注意的是，同一句话，采取基本模式和变体模式，它们的含义基本相同，但句子的侧重点有所不同。例如：

　　基本模式：I haven’t seen a car as old as this for years.(重点在名词car)

　　变体模式：I haven’t seen as old a car as this for years.(重点在形容词old)

　　三、as...as结构常用于形象比喻中：

　　as rich as a jew 极其富有 as cool as cucumber 沉着冷静

　　as light as a feather 轻如鸿毛 as soft as butter 性格软弱

　　as poor as a church mouse 一贫如洗 as clear as crystal 清澈透明，一清二楚

　　as busy as a bee 忙忙碌碌 as easy as ABC 相当容易

　　as deep as a well 高深莫测 as stubborn as a mule 非常顽固，倔脾气