Use an apostrophe to mark the possessive form of nouns and some pronouns, the omission of letters or figures, and in some cases, the plural of letters or figures.

P7-a Use an apostrophe to show the possessive form of a noun.

The form of a possessive noun depends on whether it is singular (one item) or plural (two or more items).

Add -’s to a singular noun to show possession.

Be sure to include the apostrophe and to place it before the -s so that the reader does not mistakenly think that the noun is plural.

Indicate shared or joint possession by adding -’s to the final noun in a list; indicate individual possession by adding -’s to each noun.

Indicate possession by adding -’s to the last word in a compound.

Even if a singular noun ends in s, add an apostrophe and -s.

If the second s makes the word hard to pronounce, it is acceptable to add only an apostrophe.

To make plural nouns possessive, add -’s if the noun does not already end in s, and add only an apostrophe if it does.

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Note: Form the plural of a family name by adding -s without an apostrophe (the Harrisons); add the apostrophe only to show possession (the Harrisons’ house).

P7-b Add an apostrophe to show where letters or figures are omitted from a contraction.

P7-c Check your style guide to determine whether to include an apostrophe to form the plural of a number, a letter, or an abbreviation.

Some style guides encourage writers to form the plural of a number, a letter, or an abbreviation by adding -’s.

However, the MLA Handbook (the most commonly used style guide in courses in English literature and composition) does not. So check with your instructor to be sure what is appropriate.

P7-d Add -’s to form the possessive of an indefinite pronoun but not a personal pronoun.

The possessive forms of personal pronouns, however, do not have apostrophes: my, mine, your, yours, her, hers, his, its, our, ours, their, theirs.

P7-e Omit unnecessary or incorrect apostrophes.

Watch for an apostrophe incorrectly added to a plural noun ending in s when the noun is not a possessive.