The apostrophe has two main functions: to indicate the omission of letters or numerals and to form a possessive. It is occasionally, but rarely, used to make a plural.
Indicating omitted letters or numerals
Apostrophes can signal the omission of one or more letters in a word, or one or more digits in a number.
The most common use is in forming contractions of verbs (I’m, it’s, they’re). Common contractions sound friendlier and less formal than the spelled-out verb and are generally preferable as long as they don’t confuse the reader.
- Spelling out a verb phrase (like cannot, do not, and must not) can be useful: Do not can add emphasis to warning messages, for example. And cannot, does not, and other negative forms can be clearer and appear more formal and authoritative than their contractions.
- Less common contractions such as would’ve and that’d may be less immediately understandable, especially for readers who aren’t native English speakers.
Apostrophes stand in for omitted letters in representations of dialect and speech so that the text more closely resembles common pronunciations. A word of warning, though: Few writers outside of Mark Twain can pull this off successfully. Most readers find text that’s written in dialect annoying.
Knowing when to hold ’em and when to fold ’em, poker upped the ante with its World Series.
This flick will be rockin’ and reelin’ in theaters next month.
Apostrophes can also indicate omitted numerals. When you cite a decade of years, use an apostrophe to indicate the omitted century. Be sure to use an apostrophe () and not a single opening quotation mark ().
The first baby boomers were born in the late ’40s.
With a few exceptions, form possessives like this:
- For most singular nouns, add an apostrophe and an s (’s) to the end of the word.
- For plural nouns that don’t already end in s, add an apostrophe and an s (’s) to the end of the word.
- For plural nouns that already end in s, just add an apostrophe.
Plural nouns that don’t end in s
Plural nouns that already end in s
the cyclist’s urine test
the players’ scores
the campus’s science building
the Phippses’ new house
George Lucas’s latest film
the witnesses’ statements
Mr. Phipps’s new house
the boxes’ contents
the witness’s testimony
the box’s contents
Exceptions to the general rules:
- For names that end with an eez sound, use an apostrophe alone to form the possessive.
According to Jones’s review, the computer’s graphics card is its Achilles’ heel.
- For singular proper nouns that are formed from a plural word (such as United Nations), use an apostrophe alone to form the possessive: United Nations’. (But use an apostrophe and an s to form the possessive of their abbreviations: U.N.’s.)
the New York Dolls’ back catalog
the United States’ foreign policy
General Motors’ CEO
the U.S.’s foreign policy
- Don’t use an apostrophe when forming any possessive pronoun, including its, yours, hers, ours, and theirs.
Usually, plurals should not have an apostrophe, even if they are abbreviations or numbers. ATMs, Drs., and 1990s are all correct. (See “Acronyms and Other Abbreviations” for more examples.)
Exception: Use an apostrophe in the plurals of letters and words if those plurals would be confusing without it. (Single letters in particular can look confusing without the apostrophe.)
Samara walked me through the do’s and don’ts of project management.
Do it now—no ifs, ands, or buts.
Enough with the thank-yous!
I’m rooting for the Oakland A’s baseball team this year. (“A’s” without the apostrophe could look like the word “as.”)
I got straight B’s on my report card this semester. (“B’s” without the apostrophe could look like the abbreviation for a potentially offensive word.)
Dot your i’s and cross your t’s.
The three R’s
ADVANCED APOSTROPHES: THE GENITIVE
A genitive can indicate:
- The source, as in the buyer’s counteroffer
- The agent, as in the fielder’s error
- The object of an action, as in the child’s rescue
- The purpose, as in ladies’ lingerie
- A type, as in a doctor’s appointment
- Length, as in two weeks’ vacation
Careful writers use an apostrophe in such cases: teachers’ union rather than teachers union.
The genitive has two quirks: First, you can use it without the primary noun, as in We are going to the doctor’s. Second, you can use it after of to indicate possession. A dream of Jeannie (not the genitive) is different from a dream of Jeannie’s. In this case, the genitive noun (here, Jeannie) must be a living thing or a person, and the word before of (dream) must constitute only a part of the whole (all of Jeannie’s dreams). Thus, you’d write a friend of Bill’s—because Bill has many friends—and not a friend of Bill, the same as you’d write a friend of his and not a friend of him.