The Punctuation Guide.com

Apostrophe

The apostrophe ( ’ ) has three uses: contractions, plurals, and possessives.

Contractions

Contractions (e.g., let’s, don’t, couldn’t, it’s, she’s) have a bad reputation. Many argue that they have no place at all in formal writing. You should, of course, observe your publisher’s or instructor’s requirements. An absolute avoidance of contractions, however, is likely to make your writing appear stilted and unwelcoming.

If you are unsure where to insert the apostrophe when forming a contraction, consult a good dictionary.

Avoid two of the most common contraction–apostrophe errors: the contraction of it is is it’s, and the contraction of let us is let’s; without the apostrophe, its is the possessive form of it, and lets is a form of the verb let, as in “to allow or permit.”

Examples

It’s often said that every dog has its day.

Let’s not forget that grandma lets the kids eat way too much junk food when they stay with her.

In informal writing, it is acceptable to indicate a year with only the last two digits preceded by an apostrophe (e.g., the class of ’85, pop music from the ’80s).

Plurals

The apostrophe is seldom used to form a plural noun.

Correct

Since the 1980s, the Thomases, both of whom have multiple PhDs, have sold old books and magazines at the fair on Saturdays and Sundays.

Incorrect

Since the 1980s, the Thomass, both of whom have multiple PhDs, have sold old books and magazines at the fair on Saturdays and Sundays.

The rare exception to the rule is when certain abbreviations, letters, or words are used as nouns, as in the following examples. Unless the apostrophe is needed to avoid misreading or confusion, omit it.

Examples

He received four A’s and two B’s.

We hired three M.D.’s and two D.O.’s.

Be sure to cross your t’s and dot your i’s.

Do we have more yes’s than no’s?

For this last example, the trend is to instead write yeses and noes.

Possessives

The formation of possessives is treated in different ways by different authorities. The rules below are based on The Chicago Manual of Style, 17th edition, and are appropriate for most writing. Associated Press style, used by most newspapers, is slightly different. See the essay on style for more information.

The general rule for forming possessives

The general rule is that the possessive of a singular noun is formed by adding an apostrophe and s, whether the singular noun ends in s or not.

Examples

the lawyer’s fee

the child’s toy

the girl’s parents

Xerox’s sales manager

Tom Jones’s first album

Jesus’s disciples

Aeschylus’s finest drama

JFK’s finest speech

anyone’s guess

a week’s vacation

Texas’s oil industry

The possessive of a plural noun is formed by adding only an apostrophe when the noun ends in s, and by adding both an apostrophe and s when it ends in a letter other than s.

Examples

excessive lawyers’ fees

children’s toys

the twins’ parents

the student teachers’ supervisor

the Smiths’ vacation house

the Joneses’ vacation house

the boys’ baseball team

the alumni’s fundraising

three weeks’ vacation

someone with twelve years’ experience

Exceptions to the general rule

Use only an apostrophe for singular nouns that are in the form of a plural⁠—or have a final word in the form of a plural⁠—ending with an s.

Examples

Beverly Hills’ current mayor

the United States’ lingering debt problem

Cisco Systems’ CEO

the Beatles’ first album

Nouns that end in an s sound take only an apostrophe when they are followed by sake.

Examples

for goodness’ sake

for conscience’ sake

A proper noun that is already in possessive form is left as is.

Examples

McDonald’s menu was simplified in response to COVID-19.

Sainsbury’s and Tesco’s produce quality has never seemed to me as good as Waitrose’s.

Shared or individual possessives

Joint possession is indicated by a single apostrophe.

Example

This course will use Robert Smith and Rebecca Green’s psychology textbook.

Explanation: They coauthored the book.

Example

We were at Stanley and Scarlett’s house.

Explanation: They share the house.

Individual possession is indicated by apostrophes for each possessor.

Examples

France’s and Italy’s domestic policies are diverging.

Chris’s and John’s houses were designed by the same architect.

Avoid awkward possessives

Awkward

Correct but awkward: Let’s meet at St. Patrick’s Cathedral’s Fifth Avenue entrance.

Better

Better: Let’s meet at the Fifth Avenue entrance for St. Patrick’s Cathedral.

The apostrophe with other punctuation

The apostrophe should never be separated from the word to which it attaches by adjacent punctuation.

Correct

The house on the left is the Smiths’, but the house at the end of the street is the Whites’.

Incorrect

The house on the left is the Smiths,’ but the house at the end of the street is the Whites.’