Apostrophes are a form of punctuation that have two main uses: to show possession and to indicate missing letters in contractions.

Using Apostrophes to Show Possession

Apostrophes and Singular Nouns  

  • If the noun ends in any letter except s, add ’s.  
    • e.g., I put the student’s essay in the drop box. (one student) 
  • If the singular noun ends in s, you can choose whether to add ’s or just an apostrophe. It doesn’t matter which you choose, but you should be consistent throughout your piece of writing. 
    • e.g., Mr. Jones’s car or Mr. Jones’ car; a waitress’s wages or a waitress’ wages 

Apostrophes and Plural Nouns 

  • If the noun ends in s, add only an apostrophe.  
    • e.g., I put the students’ essays in the drop box. (many students) 
  • If the plural noun ends in a letter other than s, add ’s.  
    • e.g., She tried out for the women’s hockey team. 

Apostrophes in Contractions

A contraction is a word where a letter or two have been left out, largely due to ease of pronunciation. 

e.g., did not = didn’t; would have = would’ve; we are = we’re.  

Contractions are generally considered to be informal. Usually, they are appropriate in spoken and professional communication but are to be avoided in academic writing.

Other Uses of Apostrophes

Use apostrophes to form the plural of lowercase letters, abbreviations with periods, and some uppercase letters.  

  • e.g., There are six s’s in the word “dispossesses.” 
  • e.g., B.A.’s are no longer a guarantee of a good job. 
  • e.g., Mary received straight A’s throughout high school. 

For acronyms, numbers, decades, and words used as words, you can add or omit the apostrophe (just be consistent). However, the current trend is to omit them in such cases. 

  • e.g., CEOs or CEO’s; 7s or 7’s; 1990s or 1990’s; ands or and’s 

Avoiding Apostrophe Errors

Incorrect apostrophe use can completely change the meaning of a sentence:

Incorrect Use Correct Use
The announcer called the players names as each one stepped onto the ice. Was the announcer insulting the players or simply announcing their names? The announcer called the players’ names as each one stepped onto the ice.
A large pane of glass came loose in the heavy wind and narrowly missed the worker’s heads. Was there only one worker who had more than one head? A large pane of glass came loose in the heavy wind and narrowly missed the workers’ heads.
Financial Advisors: Were Here to Help! The advisors were here but have all gone on vacation? Financial Advisors: We‘re Here to Help!

Common Apostrophes Mistakes

Do not use apostrophes with possessive pronouns: his, hers, its, ours, yours, theirs, whose. 

  • e.g., Is that car yours? (NOT your’s) 
  • e.g., The company has relocated its head office. (NOT it’s) 
  • e.g., Is that the man whose beard caught on fire when he tried to light his cigar? (NOT who’s) 

The most common mistake in using apostrophes involves the confusion between it’s, which means it is or it has, and its, which is a possessive pronoun.

Do not use apostrophes with regular plural nouns that do not show possession.  

  • e.g., The Jamiesons finally visited Scotland. (NOT the Jamieson’s) 
  • e.g., Glen Gould owned several pianos. (NOT piano’s) 

Not every problem with apostrophes will result in a communication disaster, but remember that some readers have a zero-tolerance approach to their misuse. Even when apostrophe errors do not cause confusion, their presence demonstrates a lack of attention to proofreading, which detracts from the professionalism of your writing.