關系代詞所代替的先行詞是人或物的名詞或代詞，并在句中充當主語、賓語、定語等成分。關系代詞在定語從句中作主語時，從句謂語動詞的人稱和數要和先行詞保持一致。

1)who， whom， that

這些詞代替的先行詞是人的名詞或代詞，在從句中作主語和賓語。例如：

Is he the man who/that wants to see you? 他就是你想見的人嗎?(who/that在從句中作主語)

He is the man whom/ that I saw yesterday. 他就是我昨天見的那個人。(whom/that在從句中作賓語)

2) whose 用來指人或物，(只用作定語， 若指物，它還可以同of which互換)。例如：

They rushed over to help the man whose car had broken down.那人車壞了，大家都跑過去幫忙。

Please pass me the book whose (of which) cover is green.請遞給我那本綠皮的書。

3)which， that所代替的先行詞是事物的名詞或代詞，在從句中可作主語、賓語等。例如：

A prosperity which / that had never been seen before appears in the countryside.

農村出現了前所未有的繁榮。(which / that在句中作賓語)

The package (which / that)you are carrying is about to come unwrapped. 你拿的包快散了。(which / that在句中作賓語)