Use an apostrophe to show singular possession (“The doctor’s office was always busy”) and plural possession (“The doctors’ offices were always busy”).

Note: The use of an apostrophe can be determined by inserting an of phrase, as in “The offices of the doctors were busy.”

If the noun is singular, add “s”:

• “I enjoyed Betty’s presentation.”
• “Someone’s coat is in the lobby.”

The same applies for the singular nouns ending in “s,” like James: “This is James’s new office.”

Use an apostrophe to show possession of two objects by two people. “Hilda’s and Janet’s cars were crushed by the falling tree.”

Use only one apostrophe when a possession is shared by two people. “Robert and Susan’s house sold in five hours.”

Use an apostrophe to show possession in words that are already plural. “The women’s changing room at the gym was being renovated.” Or, “The men’s changing room had been renovated last year.”