关系副词 where丶when 和 why 可以放在句中，也可以加在子句。在正式书写上，一般会用到「介系词 which」的句型，用关系副词则是较普遍的用法。
| 引导关系子句的「介系词 which」结构，较正式 | 使用关系副词的结构，较为普遍 |
|---|---|
| that's the restaurant in which we met for the first time. | that's the restaurant where we met for the first time. |
| that picture was taken in the park at which i used to play. | that picture was taken in the park where i used to play. |
| i remember the day on which we first met. | i remember the day when we first met. |
| there was a very hot summer the year in which he was born. | there was a very hot summer the year when he was born. |
| tell me the reason for which you came home late. | tell me (the reason) why you came home late. |
| do you want to know the reason for which he is angry with sally? | do you want to know (the reason) why he is angry with sally? |