When do I use "Who" and when do I use "Whom"?

Who = subject (does the action, like he/she). Whom = object (receives the action, like him/her). After a preposition (to, for, with, by): always "whom."

What is the most common mistake with "Who" and "Whom"?

"Who did you call?" is very common but should be "whom did you call?" (you called him/her, not he/she). In informal spoken English, "who" is increasingly accepted in object position; in formal English and after prepositions ("to whom," "for whom"), "whom" is required.

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Which one to use?Advancedpronombrepronombre

WhovsWhom

"Who" is the subject (does the action); "whom" is the object (receives the action).

Side-by-side comparison

Who

pronombre

"Who" is the subject pronoun for people. "Who called?" = which person made the call? Swap test: if "he" or "she" fits in the answer, use "who". "The person who called" = she called.

Who called me while I was in the meeting?
The woman who lives next door is a doctor.
Who is going to present the project tomorrow?

Whom

pronombre

"Whom" is the object pronoun for people. "Whom did you call?" = which person did you call? Swap test: if "him" or "her" fits, use "whom". Always required after prepositions: "to whom", "with whom".

To whom should I address this letter?
The candidate whom the committee selected has ten years of experience.
With whom did she travel to the conference?

Common mistake

•"Who did you call?" is very common but should be "whom did you call?" (you called him/her, not he/she).
•In informal spoken English, "who" is increasingly accepted in object position; in formal English and after prepositions ("to whom," "for whom"), "whom" is required.

Trick to remember it

Substitution test: answer with "he/she" or "him/her." If the answer uses "he/she" = "who"; "him/her" = "whom." "Who/whom called?" → "he called" = "who." "Who/whom did you call?" → "I called him" = "whom."

Quick rule

•Who = subject (does the action, like he/she).
•Whom = object (receives the action, like him/her).
•After a preposition (to, for, with, by): always "whom."

Did you know?

WHOM is in the process of going extinct in spoken English. Linguists predict that in a few generations it will disappear from everyday speech and remain only in formal and legal texts, just as "thee" and "thou" (the Old English "you" singular) already did. For now, using it correctly in formal writing signals a high level of language mastery. The irony is that many native speakers hypercorrect and use WHOM where WHO belongs: "Whom shall I say is calling?", wrong; here WHOM is the subject of the subordinate clause, not the object, so WHO is correct.