一、基本概念 

关系副词的意思相当于“介词+which结构”，在定语从句中做状语的成分。

1.He will always remember the day when/on which his father returned from America.

他将永远记得父亲从美国返回的那一天

拆分后：

He will always remember the day.

His father returned from America on the day..

2.This was the time when/at which she left for Beijing.

这就是她动身去北京的时间。

拆分后

This was the time.

She left for beijing at the time.

3.I don’t know the reason why/for which he didn’t come to the meeting yesterday morning.

我不知道他为什么没有参加昨天上午的会议。

I don’t know the reason.

He didn’t come to the meeting yesterday morning for the reason.