where做定语从句的用法如下：
一、where引导定语从句时,where是关系副词,在从句中作地点状语,其前面有表示地点的先行词，where引导的从句修饰先行词.例如：
The bookshop where I bought this book is not far from here.
This is the house where I lived two years ago.
We will start at the point where we left off.
二、where引导状语从句时,where是从属连词,where引导的从句修饰主句的谓语动词，where前面没有表示地点的先行词.例如：
Wuhan lies where the Changjiang River and the Han Jiang Rivermeet.
Make a mark where you have any doubts or questions.
I found my books where I had left them.
有时,where引导的地点状语从句兼有抽象条件含义,可放在主句的前面,而where引导的定语从句则不能.例如:
Where there is a will,there is a way.〔谚语〕有志者事竟成.
Where there is water,there is life.有水的地方就有生命.
三、在有些情况下,where引导的定语从句可转换为where引导的地点状语从句.例如：
A tall building was put up at the place where there used to be adesert.（＝A tall building was put up where there used to be adesert.）在以前曾是沙漠的地方盖起了一幢高楼.