The primary functions for apostrophes are to form possessives and to stand in for missing letters in a contraction. Apostrophes are only very rarely used to form plurals.
- Use possessive forms when you want to indicate ownership, or “belonging to.” Possessives are almost always formed by adding an apostrophe and an “s” to the end of a noun (a person, place, or thing).
- Mike’s bike is in the yard.
- Phoenix’s temperatures bring lots of visitors in winter.
- The table’s legs were broken.
- Remember, add an “’s” when the noun does not end in an “s” (driver’s) or when the noun is singular and ends in an “s” (Lois’s).
- If the noun is plural but not possessive and ends in “s,” you don’t need to add an apostrophe (diplomas instead of diploma’s).
- Nouns also change to express possession (ownership) by using an apostrophe followed by the letter “s” (’s). This can denote singular or plural possessive.
Following are examples of possessive apostrophe use:
- The student’s attempts to solve the problem were rewarded.
The above sentence means one student made an attempt.
- The students’ attempts to solve the problem were rewarded.
The above sentence means more than one student made an attempt.
If you are making an irregular plural noun possessive, the apostrophe comes before the “s” because the word is already plural.
- children/children's (plural)
If a singular common noun ends in “s,” add “’s.”
- The boss’s temper was legendary among his employees.
- The witness’s version of the story has several inconsistencies.
Proper nouns ending in “s” differ depending on whether you refer to the Chicago Manual of Style or, say, the Associated Press Stylebook.
- Chris’s book was lost. (Chicago Manual of Style)
- Chris’ book was lost. (Associated Press Stylebook)
Apostrophes with Compound Nouns
If a compound noun uses dashes, place the apostrophe after the last noun.
- My brother-in-law’s house backs up to Tonto National Forest.
If there is a compound noun, add the possessive apostrophe to the last noun.
- I went to see Anthony and George's new apartment.
The apartment belongs to both Anthony and George.
If the compound noun indicates individual possession, add the apostrophe to both nouns. For example, if you have a compound subject, like Jose and Anna, and they own something together, it would look like this:
- Jose and Anna’s home is on Third Street.
However, if Jose and Anna have different homes, it would look like this:
- Jose’s and Anna’s homes are on Third Street.
Here are a few more possessive examples:
- The amendment’s language clarifies the terms left undefined in the original law.
In this case, “language” corresponds to “amendment”; “terms” is plural.
- A review of the month’s headlines reveals nine front-page pieces about the local school board election.
Here, “headlines” correspond to “month”; “headlines” and “pieces” are plural.
- Sara Jones’s study of language use and class is considered a classic in the field.
- “Study” corresponds to “Jones”; the apostrophe ’s must be added to a proper noun that ends in “s”
A Word About Confusion with Plurals and Possessives
Plural words that end in “s” are not necessarily possessive so do not take apostrophes.
- Three key ideas emerged in the introduction.
- The organization was restructured after decades of poor performance.
- All animals have an innate evolutionary drive to pass along genes to offspring.
But plurals that are also possessive do use apostrophes. Notice how the position of the apostrophe moves depending on whether the plural ends with “s” or not.
- The book traces the Kennedys’ influence on national politics.
- The library science degree offers a special emphasis in children’s literature.
- The board changes the policy after the stakeholders’ objections.
Apostrophes and Missing Letters
Apostrophes are also used to stand in for missing letters in a contraction:
- The conclusion doesn’t [does not] follow from the evidence.
- Remove the test tubes from the sterilizer when the cycle’s [cycle is] finished.
- This committee will file a final report when we’re [we are] done with the applications.
In addition, apostrophes are used to stand for missing letters in “shortened” or slang words:
- ’Tis [it is] the season to be jolly.
Do not use an apostrophe to form the plurals of numbers or acronyms.
- three CEOs
- these JPEGs
Distinguish between plural and possessive dates.
- The 1970s’ music was the best.
The 1970s own that music.
- The 1970s are but a memory to many of us.
The 1970s is plural but does not own a memory.
Add apostrophes (or not) to the following sentences.
- Johns book is on the floor.
- The childrens playground is a next to the grocery store.
- The 1990s was a time of turmoil.
- The Smiths dog broke free from his leash.