形容词、副词有三个等级：原级、比较级和最高级，其构成形式如下：
规则变化：单音节词和少数双音节词，加词尾-er，-est来构成比较级和最高级
构成法 | 原级 | 比较级 | 最高级 |
一般单音节词未尾加-er, -est | tall | taller | tallest |
以不发音的e结尾的单音词和少数以-le结尾的双音节词只加-r,-st | nice | nicer | nicest |
以一个辅音字母结尾的闭音节单音节词，双写结尾的辅音字母，再加-er,-est | big | bigger | biggest |
"以辅音字母 y"结尾的双音节词，改y为i，再加-er，-est | busy | busier | busiest |
少数以-er,-ow结尾的双音节词未尾加-er,-est | clever narrow | cleverer narrower | cleverest narrowest |
其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 | important easily | more important more easily | most important most easily |
不规则变化
原级 | 比较级 | 最高级 |
good/well | better | best |
bad/ill | worse | worst |
old | older/elder | oldest/eldest |
much/many | more | most |
little | less | least |
far | farther/further | farthest/furthest |
注意：many, old和far比较级及最高级用法的区别
①如果后接名词时，much more 不可数名词，many more 可数名词复数。
②old有两种比较级和最高级形式: older/oldest 和elder/eldest。elder，eldest只用于兄弟姐妹的长幼关系。
My elder brother is an engineer.//Mary is the eldest of the three sisters.
③far有两种比较级，farther，further..
