当它在该定语从句中充当主语成分时，就是主语。如： i have a book which is about animals. 该句中的which是修饰book的，你把它换成book后放到从句中，就变成了the book is about animals.这样你就可以判断出它就是从句的主语。 宾语也是一样。如： this is the gift which my father gave to me. which修饰gift，= my father gave the gift to me. 所以which是gave的宾语。
The person who gave us a lecture last week was a actor.主语 The person whom I knocked down with my bike yesterday is still in hospital.宾语 The person whose eieter is my new girlfriend is the chief engineer of the company.定语本回答被提问者采纳