Who whose and whom difference same sentences?

"Who" is used as a subject in a sentence, while "whom" is used as an object. For example, in the sentence "Who is coming to dinner?" "who" is the subject. In contrast, in "To whom should I address the letter?" "whom" is the object of the preposition "to." "Whose" is a possessive form, as in "Whose book is this?" indicating ownership.