Whom can be used instead of who when it is the object of a verb or preposition. It can be used in the following ways: 作動詞或介詞的賓語時，who可以用whom來替換。whom 有以下用法

as a relative pronoun (referring back to a person and starting a relative clause): 用作關系代詞（回指人並引導關系從句）: Students for whom English is a second language should consider taking the course. 以英語作爲第二語言的學生應該考慮上這門課。 The book was written by his wife, Joan, whom he married in 1962. 這本書是由他的妻子瓊寫的，他與她在1962年結婚。 (starting a relative clause that is the subject, object, or complement of another clause): 引導作另一分句的主語、賓語或補語的關系從句: I don't know whom you've already met. 我不知道你已經碰見過誰。

as a question pronoun: 用作疑問代詞: Whom do you blame? 你怪誰呢？

Whom is only used in written English and in formal spoken English. Who is normally used as the object of a verb or preposition, but immediately after a preposition whom is generally used: whom 只用於書面語和正式口語中。who 常用作動詞或介詞的賓語，但緊接在介詞後時一般用whom: the man with whom she lived. 跟她同住的那個男人。 It would, however, be more natural to say: 但常常這樣說更自然: the man she lived with 跟她同住的那個男人。.