英语中常用的关系代词有:which、that、who、whom、whose。根据这些代词在句中的句法功能,可以把它们分为主格、宾格和所有格三类,即:
主格:which、that、who
宾格:which、that、who、whom
所有格:whose
which引导定语从句时,在从句中既可以作主语,也可以做宾语。如:
Yesterday I lost the book which my English teacher had given me as a birthday gift. (作宾语)
Yesterday I lost the book which had been given to me by my English teacher as a birthday gift. (作主语)