when指时间
在定语从句中做时间状语也可做连接词用
(1) I still remember the day when I first came to the school.
(2) The time when we got together finally came.
where指地点
在定语从句中做地点状语
(1) Shanghai is the city where I was born.
(2) The house where I lived ten years ago has been pulled down.
why指原因
在定语从句中做原因状语
(1) Please tell me the reason why you missed the plane.
(2) I don’t know the reason why he looks unhappy today.
注意：关系副词引导的从句可以由“介词+关系代词”引导的从句替换
(1) The reason why/ for which he refused the invitation is not clear,
(2) From the year when/in which he was going to school he began to know what he wanted when he grew up.