The possessive case denotes ownership or possession of one thing by another.

Singular nouns and indefinite pronouns

Add an apostrophe and -s to form the possessive of most singular nouns, including those that end in -s, and of indefinite pronouns (31d). Do not use apostrophes with the possessive forms of personal pronouns: yours, his, hers, its, ours, theirs.

The bus’s fumes overpowered her.

Star Wars made George Lucas’s fortune.

Anyone’s guess is as good as mine.

Plural nouns

To form the possessive case of plural nouns not ending in -s, add an apostrophe and -s.

The men’s department sells business attire.

For plural nouns ending in -s, add only the apostrophe.

The three clowns’ costumes were bright green and orange.

Compound nouns

For compound nouns, make the last word in the group possessive.

The secretary of state’s speech was televised.

Both her daughters-in-law’s birthdays fall in July.

My in-laws’ disapproval dampened our enthusiasm for the new house.

Two or more nouns

To signal individual possession by two or more owners, make each noun possessive.

Great differences exist between Jerry Bruckheimer’s and Ridley Scott’s films.

Bruckheimer and Scott have produced different films.

To signal joint possession, make only the last noun possessive.

Wallace and Gromit’s creator is Nick Park.

Wallace and Gromit have the same creator.