Possessive nouns usually indicate ownership, as in Tim’s hat or the lawyer’s desk. Frequently, however, ownership is only loosely implied: the tree’s roots, a day’s work. If you are not sure whether a noun is possessive, try turning it into an of phrase: the roots of the tree, the work of a day. (Pronouns also have possessive forms. See below and P4-d.)
When to add -’s
Luck often propels a rock musician’s career.
The Children’s Defense Fund is a nonprofit organization that supports programs for poor and minority children.
Lois’s sister spent last year in India.
Her article presents an overview of Marx’s teachings.
note: To avoid potentially awkward pronunciation, some writers use only the apostrophe with a singular noun ending in -s: Sophocles’.
When to add only an apostrophe
If the noun is plural and ends in -s, add only an apostrophe.
Both diplomats’ briefcases were searched by guards.
Joint possession
To show joint possession, use -’s or (-s’) with the last noun only; to show individual possession, make all nouns possessive.
Have you seen Joyce and Greg’s new camper?
John’s and Marie’s expectations of marriage couldn’t have been more different.
Joyce and Greg jointly own one camper. John and Marie individually have different expectations.
Compound nouns
If a noun is compound, use -’s (or -s’) with the last element.
My father-in-law’s memoir about his childhood in Sri Lanka was published in October.
Indefinite pronouns
Indefinite pronouns refer to no specific person or thing: everyone, someone, no one, something. (See B1-b.)
Someone’s raincoat has been left behind.