英语定语从句的用法大全（三）
今天接着跟大家分享英语定语从句中关系副词的用法。
五、关系副词
英语里常见的关系副词有when、where、why。
（一）when
when用作关系副词时，先行词都是表时间的，此时when在定语从句中作时间状语。如
I will never forget the days when we spent our summer holiday in the mountainous village.
此时的when相当于“介词+which”的用法。如上句可以改为：
I will never forget the days during which we spent our summer holiday in the mountainous village.
【注意】
1、尽管先行词是表时间的，但有的时候也会使用关系代词来引导定语从句，此时关系代词往往在从句中充当宾语。如：
I will never forget the days that/which we spent together in the mountainous village.
关系代词that/which，用作从句中的谓语动词spent的宾语。
2、when有时也会用来引导非限定性定语从句，但有时也会使用“介词+which”的结构。如：
He was born in 1976, when some of China's great leaders passed away.
I just can't forget my childhood days, some of which have already had their longlasting influence upon my present life.
（二）where
where用作关系副词时，先行词都是表地点的，此时where在定语从句中作地点状语。如：
This is the house where the soldiers once took shelter from the enemies.
与when的用法相似的是，此时的where相当于“介词+which”的用法。如上句可以改为：
This is the house in which the soldiers once took shelter from the enemies.
【注意】
1、与when的用法相似的是，尽管先行词是表地点的，但有的时候也会使用关系代词来引导定语从句，此时关系代词往往在从句中充当宾语。如：
This is the house that/which we visited last year.
关系代词that/which，用作从句中的谓语动词visited的宾语。
2、同样与when的用法相似的是，where有时也会用来引导非限定性定语从句。此时的where也常可以用“介词+which”的结构来替换。如：
My brother works in a faraway mountainous town, where he can always enjoy a stunning view of the beautiful mountains.
句中的where就可以替换为from which，即：
My brother works in a faraway mountainous town, from which he can always enjoy a stunning view of the beautiful mountains.
（三）why
与when和where不同的是，why用作关系副词引导定语从句时，其先行词一定是reason，而且只能用在限定性定语从句中，即中间不能用逗号隔开。如
That is the reason why he has left for Shanghai.
【注意】
在现代英语中，why也经常可以省略。如：
This is the reason I opened the window at this time of the day.
六、定语从句转换为短语
有时出于结构简洁的需要，定语从句可以转化为短语结构。
不过，不是所有的定语从句都可以转化为短语结构的，一般只有当关系代词在从句中充当主语的时候才可以转化为短语。如：
定语从句1：The woman who is standing behind the counter served me just now.
短语结构1：The woman standing behind the counter served me just now.
定语从句2：The woman who served me just now is standing behind the counter.
短语结构2：The woman serving me just now is standing behind the counter.
定语从句3：The woman who has already left served me just now.
短语结构3：The woman having already left served me just now.
【注意】
当关系代词在从句中充当主语时，也有的情况下是不能转化为短语的，一般是当从句的谓语动词中含有情态动词或will或would等助动词时。如以下两句话中的定语从句就不能转化为短语结构：
The woman who can dance is Jack's mother.
The woman who will visit her is her aunt.
七、用法小结
八、小测试
好了，下面大家就来做个小测试，看看前面分享的内容你都记住了多少吧。