Question 1

What's the difference between "who" and "whom"?

Accepted Answer

Who is the subject — it does the action. Whom is the object — the action happens to it. Swap in he or him as a test. If the sentence works with he, use who ("Who called?" — he called). If it works with him, use whom ("To whom did you speak?" — you spoke to him). The m in whom and him is your reminder. The whom form has been quietly fading from spoken English for a century — linguists call it an "object-case pronoun on the way out." It survives in formal writing, in fixed phrases (to whom it may concern), and in cover letters, where using it correctly still reads as careful and literate. Exception: In speech, who is acceptable almost everywhere whom would be strictly correct — nobody says whom did you see. The rule mostly matters in edited prose, legal writing, and formal correspondence.

Question 2

When do I use "whom"?

Accepted Answer

Use whom when the pronoun is the object of a verb or preposition — when something is done to it.

Question 3

Is it "who to blame" or "whom to blame"?

Accepted Answer

"Whom to blame." The blame is being done to someone — the object slot calls for whom.

Question 4

Is it "who should I call" or "whom should I call"?

Accepted Answer

Strictly, "whom should I call" — the caller is doing the calling to someone.