Use apostrophes to form the possessive case of nouns and to indicate a missing letter in a contraction.

Form the possessive case of a singular noun by adding an apostrophe and an s, even if the singular noun ends in s, x, or z. For plural nouns that end in s, form the possessive case by adding only an apostrophe.

Microsoft style

insider’s guide

the box’s contents

Burns’s poems

Berlioz’s opera

an OEM’s product

the Joneses’ computer

Differentiate between the contraction it’s (it is) and possessive pronoun its. Never use an apostrophe with possessive pronouns (yours, not your’s).

Do not use an apostrophe to indicate the plural of a singular noun (programs, not program’s).