easy 简单的，容易的
[例句]这是一篇容易的课文。
[错误]It is an easy text to learn.
[正确]It is a text easy to learn.
[说明]形容词（本例中的easy）带有状语短语（本例中的 to learn）时候，该形容词应连同其状语短语一起放在所修饰的名词之后。
[例句]他很容易就买到了电影票
[错误]He was quite easy to get the film tickets.
[正确]It was quite easy for him to get the film tickets.
[说明]某人做某事很容易，应用it is easy for sb. to do sth.
economical 经济的，节俭的
[例句]她是个节俭的家庭主妇
[错误]She is an economic housekeeper.
[正确]She is an economical housekeeper.
[说明]economic ,economical 虽然都有“经济的”含义，但是表示“节俭的”，则只能用economical.
elder 年长的，资格老的
[例句]他比妹妹大7岁。
[错误]He is elder than his sister by seven years.
[正确]He is older than his sister by seven years.
[说明]older,elder都是Old的比较级。区别在于，elder不能和than连用，且只能用在人身上。older可以和than连用，且可以表示人老，也可以表示东西老。