1. where指地点，在定语从句中做地点状语用来表示地点的定语从句。
(1) Shanghai is the city where I was born.
(2) The house where I lived ten y ears ago has been pulled down.
2. when引导定语从句表示时间。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.
[注]表示时间time一词的定语从句只用when引导，有时不用任何关系代词，当然也不用that引导。
By the time you arrived in London, we had stayed there for two weeks.
到你到达伦敦的时候，我们在那里已经待了两个星期。
I still remember the first time I met her. 我仍然记得我第一次见到她。
Each time he goes to business trip, he brings a lot of living necessities, such as towels, soap, toothbrush etc。
每一次他去出差，他带来了生活必需品，如毛巾，肥皂，牙刷等，很多。
3. 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 dont 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.
注：1)介词后面的关系代词不能省略。
2)that前不能有介词。
3) 某些在从句中充当时间，地点或原因状语的介词+关系词结构可以同关系副词when ,where和why 互换。
This is the house in which I lived two years ago.
This is the house where I lived two years ago.
Do you remember the day on which you joined our club?
Do you remember the day when you joined our club?
This is the reason why he came late.
This is the reason for which he came late.
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