When to Use "Who" vs. "Whom"

Understanding when to use who versus whom depends on their grammatical roles in a sentence.

1. Who — Subject of a verb

• Use who when referring to the subject of a clause or sentence.
• The subject is the person or thing doing the action.

Examples:

• Who is coming to the party?
  (Who = subject doing the action "is coming")

• Do you know who called me?
  (Who = subject of "called")

2. Whom — Object of a verb or preposition

• Use whom when referring to the object of a verb or preposition.
• The object is the person or thing receiving the action or linked by a preposition.

Examples:

• Whom did you invite?
  (Whom = object of the verb "invite")

• To whom should I address the letter?
  (Whom = object of the preposition "to")

Quick Tip to Decide

Try replacing who/whom with he/him or she/her in the sentence:

• If he/she fits, use who (subject).
• If him/her fits, use whom (object).

Example:

• Who/Whom did you see?
  → You saw him → Use whom : Whom did you see?

• Who/Whom is calling?
  → He is calling → Use who : Who is calling?

Summary Table

Role| Use| Example
---|---|---
Subject| Who| Who wrote this book?
Object| Whom| Whom did you meet yesterday?
Object of prep.| Whom| With whom are you going?

If you want, I can also provide exercises or more examples to practice!