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 1980’s, the Thomas’s, both of whom have multiple PhD’s, have sold old book’s and magazine’s at the fair on Saturday’s and Sunday’s.
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 girls’ basketball team
the women’s basketball 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.’