英語中常用的關係代詞有：which、that、who、whom、whose。根據這些代詞在句中的句法功能，可以把它們分爲主格、賓格和所有格三類，即：
主格：which、that、who
賓格：which、that、who、whom
所有格：whose
which引導定語從句時，在從句中既可以作主語，也可以做賓語。如：
Yesterday I lost the book which my English teacher had given me as a birthday gift. （作賓語）
Yesterday I lost the book which had been given to me by my English teacher as a birthday gift. （作主語）
