1、
关系代词（that, who, whom, whose, which）所代替的
先行词是人或物的名词或代词，并在句中充当主语、宾语、定语等成分。
例1. Is he the man who/that wants to see you?（who / that在
从句中作主语，指人）
例2. He is the man whom/ that I saw yesterday.（whom / that在从句中作宾语，指人）
例3. They rushed over to help the man whose car had broken down.（whose在句中作定语，指人）
例4. Please pass me the book whose (of which) cover is green.（whose在句中作定语，指物。若指物，它还可以同of which互换）
例5. The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了。(which / that在句中作carry的宾语，指物）
2、
关系副词（when, where, why, that）可代替的先行词是时间、地点或理由的名词，在从句中作状语。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6. Beijing is the place where (in which) I was born.
例7. Is this the reason why (for which) he refused our offer?
例8. His father died the year (that / when / in which) he was born.
例9. He can’t find the place (that / where / in which) he lived forty years ago.