定语从句的when
=when作为定语从句的引导词时，表示时间，在从句中充当时间状语，后面需要加上完整的陈述语序。
句式如下：
表示时间的名词+when+完整陈述句+句子其它成分。
when引导的定语从句可以放在主语，宾语或者表语，甚至为名词的宾补之后。
例：
The night when we took a stroll in the park was so cold.
咱们在公园散步的那个晚上好冷。
night 做主语，被定语从句when we took a stroll in the park 修饰。
I remember the night when we took a stroll in the park.
我记得那个咱们一起在公园散步的夜晚。
night变成了宾语，被定语从句when we took a stroll in the park修饰。
What I can never forget is the night when we took a stroll in the park.
我永不能忘记的是咱们一起在公园散步的那个夜晚。
night变成了表语，被定语从句when we took a stroll in the park修饰。
以上三组例句中，when后面所接的都是完整句，并且when 后的从句时态和主句一致。前提是when充当的从句的时间状语，相当于是at the night.
所以，以上三句，可以把when都改成at which。
写作必备when引导定语从句句式：
There was a time when...... 曾经。。。
There was a time when people were never bothered by pollution.
曾经人们不用为污染烦忧。
We all experience a day when......我们都经历过。。。
We all experience a day when everything goes wrong.
我们都经历过事事不顺心的一天。
we can never ignore the time when......我们绝不能忽视。。。
We can never ignore the time when computers penetrate our life and study.
我们不能忽视这个电脑渗透进我们的`生活和学习的年代。
关系副词引导的定语从句
关系副词可代替的先行词是表示时间、地点或理由的名词，在从句中作状语。
1)关系副词when, where, why的含义相当于"介词+which"结构，因此常常和"介词+ which"结构交替使用。
例如：
There are occasions when (on which) one must yield.
任何人都有不得不屈服的时候。
Beijing is the place where (in which) I was born.
北京是我的出生地。
Is this the reason why (for which) he refused our offer?
这就是他拒绝我们帮助他的理由吗?
2)that代替关系副词，可以用于表示时间、地点、方式、理由的名词后代替when, where, why和“介+which”引导的定语从句，在口语中that常被省略。
例如：
His father died the year (that/when/in which) he was born.
他父亲在他出生那年逝世了。
He is unlikely to find the place (that/where/in which) he lived forty years ago.他不大可能找到他四十年前居住过的地方。
