When do I use "whom"?

Answer 1

This is how I remember it: if I can replace it with "he/she"-- use WHO; if you can replace with "him/her"- use WHOM.

Example: Who bought this cake? (he did)

Whom did you see? (I saw her)-- but can use WHO in this sentence as well

"whom" is considered an outdated form and is usually substituted by WHO

Answer 2

Use who when referring to the subject, the person doing the action and use whom when referring to the object of a verb or preposition.

My favorite example is, "Who kissed whom?" In this sentence, you can clearly see the subject, who is the one doing the kissing, and the direct object whom is the one being kissed.

Here is a simple version of whom as the object of a preposition: "Who went with whom?" Who is the subject, the doer of the action, and whom is the object of a preposition.

A more complicated example: "Her best friend Artie, for whom she would walk a thousand miles, saw the whole thing." In this example, whom is the object of the preposition for. As you can see, whom can appear before the verb in the sentence. What determines that the pronoun in question will be whom instead of who is the preposition for.

A tricky one: "Whom would she go with?" As we saw in the previous example, the verb can be after the pronoun in question. What matters is who is doing the verb, and who is affected by the verb or a preposition. She is the one going. She is going with someone, and that someone is the object of the preposition, and thus not a who but a whom.

Don't get tripped up by is. "The father is who?" uses the correct pronoun. Is is a linking verb, and as such equates or renames the subject, thus sort of sharing subject status with whatever came before is.