[译] 他比他妹妹大三岁。
[误] He is elder than his sister by three years.

[正] He is older than his sister by three years.
[注] elder 主要用来指家庭成员中年龄较长的，且只能用作定语。而 older 可以用在两者之间的年龄或新旧的比较，并且既可以作定语，也可以作表语。