Apostrophe Study Guide

Updated on Sep 23, 2011


If the English language made any sense, a catastrophe would be an apostrophe with fur.

DOUG LARSON (1902–1981)


The apostrophe is also part of the small but powerful group of punctuation marks. In this lesson, you will see how they make your words contract and show possession.

We use the apostrophe to create contractions, like don't and couldn't, and to make nouns possessive, like Harry's goldfish and the rabbit's cage.


The word contract (pronounced with the stress on the second syllable—con-TRACT) means to press together or shorten. When you squeeze two words together to make another word, that's called a contraction. For instance, the words can and not can be written as the contraction can't. Many contractions are used in speech and in informal writing (formal writing etiquette discourages the use of slang and contractions).

Possessive Nouns

A possessive noun implies ownership of something by that person, place, or thing (the noun). To make a singular noun—like boy, dog, or school—possessive, add -'s.

the boy's yo-yo the school's bleachers the kite's tail


Be careful not to confuse the plural form of a noun for its possessive form.


Plural Form: His parents drove us to school.
Singular Possessive: We went to school in his parent's car.

The first sentence indicates that two parents drove to school. The second sentence indicates that the car of only one parent was driven to school.

To form the possessive of a plural noun (for example, parents) simply add an apostrophe after the final s.

Plural Possessive: We went to school in his parents' car.

This sentence implies that the car belongs to both of his parents, not just one.

This rule applies to all plural nouns ending with an s. Irregular plural nouns not ending in s (children, women, mice) follow the rule for singular possessives:

children's women's mice's


There are only a very few words whose plural is formed with an apostrophe: numbers, letters, abbreviations, and expressions like umm, uh, and hmm. For example:

Ph.D., M.D. → Ph.D.'s , M.D.'s

I have two friends who are M.D.'s and three who have Ph.D.'s.

A, B, C, → A's, B's, C's,

She received two A's and three B's on her report card this marking period.

1, 2, 3, → 1's, 2's, 3's,

Please try to write your 4's and 9's more clearly; they look too much alike.

umm, uh, hmm → umm's, uh's, hmm's

Try to avoid umm's and uh's when you are giving a speech.


Only one possessive— its—does not require an apostrophe. If you mistakenly add an apostrophe to it to make it possessive, you are actually forming the contraction meaning it is, usually creating utternonsense:

The puppy wagged it's tail. → The puppy wagged it is tail.

A practice exercise for this concept can be found at Apostrophe Practice Exercise.

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