object The part of a clause that receives the action of the verb, or the part of a phrase that follows a preposition.
preposition A word (such as between, in, or of) that indicates the relation between a word in a sentence and its object.
Two strategies can help you figure out whether to use who or whom.
Change who to whom when the pronoun is an object within another clause that has a subject and a verb.
Change who to whom when the pronoun is the object of a preposition.
Change whom to who when the pronoun is the subject of a clause and is followed by a verb.