第一看一个定语从句的例子，请看下面第一句。
①He grew up in the house [in where] he still lives with his wife.
②He grew up in the house [where] he still lives [in the house] with his wife.
③他在这所房屋里长大，他和他老婆目前仍然住在这所房屋里。
大家可以看到，在先行词where的前面，有一个介词in。倘若大家不要这个in，那样这句话应当改写成上面第二句，而第二句有一个明显的问题，那就是the house出现了两次，一次出目前主句中，一次出目前从句中，而这种同一成分在同一句子中的多次重复，正是英语的大忌，所以大家需要将in转移到where的前面，从而将第二次出现的the house省略掉，并用where代替这个被省略掉的the house，你了解了吗？下面我再举三个类似的例子，请你自己剖析一下，原理都一样，我就不罗嗦了。
①This is the book [by which] Newtons calculus1 was introduced into China.
②This is the book [which] Newtons calculus was introduced [by the book] into China.
③正是通过这本书，使牛顿的微积分介绍到中国来。
①Please contact your webmaster [from whom] you can obtain a new password.
②Please contact your webmaster [whom] you can obtain a new password [from your webmaster].
③请联系你的互联网管理员，你可以从他那里获得一个新口令。
①This is the ruler [with that] you can draw a straight line.
②This is the ruler [that] you can draw a straight line [with the ruler].
③这就是那把尺子，你可以用它划一条直线。
