Using who and whom correctly is the sign of an excellent writer. For one, the two are not interchangeable simply because they belong in different cases. And while whom may sound like a stuffy word, it actually has its proper place in good present-day grammar.
Who is a pronoun that asks what about a person or persons. Technically, it refers to people rather than animals though it often appears in that context in informal writing. You’ll see it used in both essential and nonessential clauses to introduce them in a sentence. You should always use who when writing about the subject of a clause.
Whom is the objective form of the pronoun, who. You should never use whom as the subject of a sentence. It can be an indirect or direct object of a sentence or prepositional phrase. But you should always use whom after a preposition.
Who vs whom have some formidable barriers to overcome to get their usage right. While the words are not interchangeable, they both often occur at the beginning of a sentence. That means you should take an extra moment to determine the meaning of it to decide on the correct form.
And it’s hard to get past the fact that whom sounds too formal and perhaps even archaic. That’s a huge obstacle with today’s current writing style. When it comes to who vs whom, the more familiar-sounding who is going to win out over whom. It comes across as a friendlier word and one which doesn’t risk sounding stuffy.
To use who and whom correctly, we need to go back to the reference for each one. Remember who speaks to the subject of a sentence. We can use he or she as a substitute to see if the usage is correct. Whom refers to the object of a sentence. For testing its use, we can then swap him or her for the word.
Let’s use the sentence, “Who drove the car?” Then, try switching out he or him for who to see which one is correct. For the former, we have the sentence, “He drove the car” or “Him drove the car” for the latter. It’s no problem seeing which one works best. The question refers to the subject driving the car.
Now try the same test with the sentence, “Whom are you speaking to?” We get either “You are speaking to he” or “You are speaking to him.” Yup, whom is the correct word in the right place because it identifies the object. With a simple substitution, you can always be sure you’re using the right form of who.