Who and whom both refer to people, but they differ by grammatical role. Use who for the subject of a verb, and use whom for the object of a verb or preposition. In everyday conversation, many speakers use who in places where strict grammar prefers whom, especially at the beginning of a question. This module shows how to choose correctly by identifying the role inside the clause, not by the position in the sentence.

The key distinction is role: a subject does the action or is the focus of the verb, while an object receives the action or completes a preposition. If the pronoun is the subject of its clause, choose who. If it functions as an object in its clause, choose whom. Always decide based on the role within the specific clause that contains the pronoun.

Rule	Example
Use who for a subject	Who called you last night?
Use whom for a direct object	Whom did you call last night?
Use whom after a preposition	To whom should I address the email?
Decide using the role inside the clause, not sentence position	Whom do you think they invited?

In questions, who or whom often appears at the beginning, even when it is not the subject. To choose correctly, mentally place the pronoun back into a normal statement order and see its role. If the pronoun would be he or she, use who; if it would be him or her, use whom. This is a role check, not a formality rule.

Rule	Example
If the answer is he or she, use who	Who is at the door? He is at the door.
If the answer is him or her, use whom	Whom did you see? I saw him.
If a preposition is fronted, whom is standard	With whom are you meeting?
In casual speech, who is common where whom is formal	Who are you meeting with?

In relative clauses, who and whom introduce additional information about a person. Choose who when the pronoun is the subject within the relative clause, and whom when it is the object within that relative clause. The main sentence role does not matter; only the role inside the relative clause matters. Formal writing keeps whom more consistently than conversation.

Rule	Example
Use who as subject in the relative clause	The person who called left a message.
Use whom as object in the relative clause	The person whom I called was unavailable.
If there is a subject already, the pronoun is often an object	The person whom she hired starts Monday.
In informal style, whom is often replaced by who or omitted	The person I called was unavailable.

Prepositions take objects, so whom is the traditional choice after a preposition. In formal English, the preposition may appear before the pronoun, making whom sound especially expected. In everyday English, the preposition is often left at the end, and many speakers then use who instead of whom. Both patterns exist; the more formal the sentence, the more likely whom appears.

Rule	Example
After a preposition, use whom	For whom is this package?
Fronted preposition plus whom is formal	From whom did you hear the news?
Stranded preposition is common in speech	Who did you hear it from?
If you keep the preposition, whom sounds natural	The colleague to whom I spoke agreed.

When who or whom appears before phrases like do you think, did she say, or is he sure, it often belongs to a later clause. Identify the verb that the pronoun actually relates to, then decide subject or object in that clause. A common pattern is whom as the object of the embedded verb, even though the pronoun starts the full question. This is why role checking inside the embedded clause is essential.

Rule	Example
Choose based on the embedded clause role	Whom do you think they chose? They chose him.
If it is the embedded subject, use who	Who do you think will win? He will win.
The main verb think does not determine who vs whom	Whom did she say you invited?
Replace with he or him inside the embedded clause to test	Whom do you believe she trusted? She trusted him.

Modern English treats whom as more formal and more common in writing than in speech. In conversation, who often replaces whom except when preceded by a preposition like to whom or for whom, which still sounds distinctly formal. In professional writing, academic writing, and carefully edited text, whom is used more consistently for objects. Choosing who in place of whom is rarely confusing, but it changes the tone.

Rule	Example
Whom increases formality	Whom should I contact regarding billing?
Who is normal in casual questions	Who should I contact about billing?
Preposition plus whom is strongly formal	To whom it may concern
In very informal style, you can avoid both with rephrasing	Who should I reach out to about billing?

Some sentence shapes appear frequently and make the choice predictable once you know the role. If the pronoun is followed by a verb directly, it is often the subject and uses who. If it is followed by a subject plus verb, it is often the object and may use whom. Recognizing these patterns speeds up decisions, especially in writing.

Rule	Example
Who plus verb often signals subject	Who wrote this report?
Whom plus subject plus verb often signals object	Whom did you hire?
Whom plus noun subject is common in formal questions	Whom should we invite?
After verbs like meet, call, hire, choose, the pronoun is often an object	Whom did they meet yesterday?

To choose between who and whom reliably, isolate the clause that contains the missing role and supply a temporary pronoun. If you would say he or she in that spot, use who; if you would say him or her, use whom. If there is a preposition directly linked to the pronoun, whom is the traditional object form. If the sentence feels too formal with whom, you can often rewrite to keep who without sounding incorrect in modern usage.

Rule	Example
Replace with he or she to confirm who	Who is responsible? She is responsible.
Replace with him or her to confirm whom	Whom are you emailing? I am emailing him.
If a preposition governs it, prefer whom in formal style	With whom did you speak?
Rewrite to avoid whom while staying clear	Who did you speak with?

Who is the subject form and whom is the object form, including after prepositions. The correct choice depends on the role within the relevant clause, which is especially important in questions and embedded clauses. Whom is more common in formal writing, while who is widely used in casual speech even where strict grammar prefers whom. With clause role checks and the he or him test, you can choose confidently and control the tone of your English.