Whose vs Who's

"Whose" is the possessive form of "who"; "Who's" is a contraction of "who is" or "who has." This follows the same pattern as its/it's and your/you're.

Quick Comparison

Aspect	Whose	Who's
What it is	Possessive form of "who"	Contraction of "who is" or "who has"
Function	Asks or indicates ownership	Combines "who" + "is" or "who" + "has"
Example	"Whose book is this?"	"Who's coming to dinner?"
Substitution test	Cannot be replaced with "who is" or "who has"	Can always be replaced with "who is" or "who has"
Apostrophe	No apostrophe	Always has apostrophe
Part of speech	Possessive pronoun/determiner	Contraction (pronoun + verb)

Key Differences

1. The Substitution Test (Never Fails)

Whose cannot be replaced with "who is" or "who has" without breaking the sentence:

"Whose phone is ringing?" → ✗ "Who is phone is ringing?" (nonsense)
"The person whose name I forgot..." → ✗ "The person who is name I forgot..." (doesn't work)

Who's can always be expanded to "who is" or "who has":

"Who's there?" → ✓ "Who is there?" (works perfectly)
"Who's been eating my porridge?" → ✓ "Who has been eating my porridge?" (same meaning)

2. Pattern with Its/It's and Your/You're

This pair follows the same pattern as other common confusions:

Possessive pronouns never use apostrophes: whose, its, your, their
Contractions always use apostrophes: who's (who is/has), it's (it is/has), you're (you are), they're (they are)

If you've mastered its/it's, you already know the pattern for whose/who's.

3. Grammatical Function

Whose is a possessive determiner or pronoun that shows ownership:

"Whose car is that?" (asking about ownership)
"I met someone whose sister is famous." (indicating possession)
"Whose turn is it?" (whose possession of the turn)

Who's is a subject-verb combination. It's followed by an adjective, noun, or verb phrase:

"Who's ready?" (who is ready)
"Who's the new teacher?" (who is the teacher)
"Who's been using my computer?" (who has been using)

4. Questions vs Relative Clauses

Whose appears in both questions and relative clauses:

Questions: "Whose keys are these?"
Relative clauses: "The author whose book won the prize will speak tonight."

Who's typically appears in questions (less common in relative clauses):

Questions: "Who's calling?" "Who's next?"
Informal speech: "She's the one who's always late." (casual)

5. Common Mistakes

These errors appear frequently:

✗ "Who's bag is this?" → ✓ "Whose bag is this?"
✗ "Whose coming to the party?" → ✓ "Who's coming to the party?"
✗ "I know someone who's father is a doctor." → ✓ "I know someone whose father is a doctor."
✗ "Whose ready to go?" → ✓ "Who's ready to go?"

When to Use Each

Use Whose when:

Asking about or indicating ownership or possession
You cannot replace it with "who is" or "who has"
It comes before a noun (whose book, whose idea, whose fault)
Introducing a relative clause showing possession
Examples: "whose phone," "whose responsibility," "the person whose..."

Use Who's when:

You can replace it with "who is" or "who has"
Asking about identity or presence
The word is followed by an adjective, noun, or verb
You mean "who is" or "who has"
Examples: "who's there," "who's the winner," "who's been here"

Memory Trick

WHO'S = WHO IS or WHO HAS. If you can't substitute either phrase, use "whose" instead.

Think: The apostrophe means something is missing (letters from "is" or "has"). No apostrophe = possessive.

Common Scenarios

Formal Writing

In formal writing (essays, business documents, academic papers), many style guides recommend avoiding contractions:

Formal: "Who is responsible for this project?" (not "Who's responsible...")
Formal: "Who has the authority?" (not "Who's got the authority?")

"Whose" remains the same in all contexts when showing possession:

"The committee will determine whose proposal is strongest."
"Whose signature appears on the document?"

Informal Writing and Speech

In casual contexts, "who's" is perfectly acceptable and widely used:

"Who's up for pizza tonight?"
"Who's been to this restaurant before?"
"Hey, who's calling?"

"Whose" is essential in any context when indicating possession:

"Whose jacket is on my chair?"
"I don't know whose decision that was."