What is the difference between 'who's' and 'whose'?

Answer 1

The pronoun 'who' is used for the subject of a sentence or a clause.

The pronoun 'whom' is used as the object of a verb or a preposition.
The pronouns 'who' and 'whom' are interrogative pronouns and relative pronouns.

An interrogative pronoun introduces a question. Examples:

Subjective: Who gave you the book?

Objective: To whom will you give the book? (object of the preposition 'to')

A relative pronoun introduces a relative clause (a group of words with a subject and a verb that gives information about its antecedent). Examples:

Subjective: The one who gave the partywas my neighbor.

Objective: The one from whom I received an invitation was my neighbor. (object of the preposition 'from')

Answer 2

The contractions who's is a shortened form of the pronoun"who" and the verb "is".

The contraction who's functions as the subject and verb(or auxiliary verb) of a sentence or a clause.

The pronoun "whose" is the possessive form of the pronoun "who".

The pronoun "whose" is an interrogative pronoun(introduces a question) or a relative pronoun (introduces a relative clause).

Examples:

Who's coming tonight? (Who is coming...), interrogative pronoun

The man who's coming is my uncle. (who is coming...), relative pronoun

Whose shoes are on the steps? (shoes belonging to...), interrogative pronoun

The one whose shoes are on the steps is asleep downstairs. (shoes belonging to...) relative pronoun

Answer 3

Who's is a contraction for 'who is' so the easiest way to decide which word is correct is to substitute the words 'who is' in the sentence. In the 2nd example below, it would not make sense to say 'Who is car is this?', but it does make sense in the first example 'Who is this?'.

Eg:

who's : Who's this?

whose : Whose car is this?