One of the most difficult aspects of writing is determining when and when not to use commas. To understand how to use commas, one must understand their function. A comma serves to separate words or word groups within a sentence in order to provide distinction among ideas.
The following demonstrates when to use commas.
Commas in a Series
Commas are used to separate three or more elements in a series.
Examples:
- Kathy, Mary, and Sue went to the market.
- Keith went to the gym, cut out sugar, and ate more vegetables to lose weight.
- I bought apples, oranges, and pears.
- She wants to sing, dance, or play the guitar for the talent show.
Introductory Phrases
Commas can be used with an introductory phrase to set it off from the rest of the sentence.
- In some cases, chemotherapy is not enough to combat cancer.
- Instead of taking medication, Charlotte changed her diet to prevent the onset of diabetes.
Transitional Words and Phrases
Use a comma to set off a transitional word or phrase in a sentence, whether at the beginning, the end, or the middle of a sentence.
- However, she decided not to accept the job offer.
- He never, in fact, wanted to go to college.
- He lied to protect his family, of course.
Commas with Appositives
An appositive is a word or group of words that renames, describes, or identifies a noun or pronoun. Commas are used to set off an appositive from the rest of the sentence.
- A successful professional athlete, he has secured many contracts during his career.
- Birkin bags, a display of wealth, sell for thousands of dollars.
- Wendy, a Lynchburg College student, was selected for an internship with NASA.
Commas and Nonrestrictive Clauses
Commas are used to set off nonrestrictive clauses, which are clauses that are not essential to the meaning of a sentence. Restrictive clauses, which contain information that is necessary to the sentence’s meaning, are not set off by commas.
- Identity theft, which affects about 15 million Americans annually, can be difficult to prevent. (NR)
- David Bowie, who passed in 2016, was an accomplished singer, songwriter, and actor. (NR)
- Teens who never text and drive are more likely to be overall safer drivers. (R)
- Children who grow up in low-income areas are less likely to go to college. (R)
Commas in Dates and Addresses
Commas are used to separate the day of the week (ex: Monday) from the month and the day of the month from the year. Use a comma after the year if the date does not fall at the end of the sentence. Commas are also used in addresses to separate the street address from the city and the city from the state (or country).
- He was born Thursday, May 8, 1997.
- On Thursday, May 8, 1997, Max was born.
- The office at 8 South Main Street, Lynchburg, Virginia, is a private law firm.
- The famous author used to live at 248A Lewis Avenue, London, England.
Unnecessary Commas
While knowing when to use commas is essential, knowing when not to use commas is just as important. A comma is not needed before the first item in a series, after the last item in a series, or between a subject and a verb. Do not use a comma before a coordinating conjunction that separates the two parts of a compound predicate, before a coordinating conjunction that separates the two parts of a compound subject, or before a dependent clause that follows an independent clause. Also, a comma is not needed to set off a restrictive clause.
Incorrect: The recipe calls for, eggs, milk, and flour.
Correct: The recipe calls for eggs, milk, and flour.
Incorrect: Igneous, sedimentary, and metamorphic, are the three main types of rock.
Correct: Igneous, sedimentary, and metamorphic are the three main types of rock.
Incorrect: Crayons and glue sticks, were included on the infinite list of school supplies.
Correct: Crayons and glue sticks were included on the infinite list of school supplies.
Incorrect: The young man’s fiancé threw her ring, and stormed out of the house.
Correct: The young man’s fiancé threw her ring and stormed out of the house.
Incorrect: Both the Senate, and the House of Representatives voted to pass the bill.
Correct: Both the Senate and the House of Representatives voted to pass the bill.
Incorrect: He was frustrated, because he couldn’t solve the math problem.
Correct: He was frustrated because he couldn’t solve the math problem.
Incorrect: The children, who were running in the halls, got in trouble.
Correct: The children who were running in the halls got in trouble.
A special thanks to Laurie Kirszner and Stephen Mandell’s Writing First, published by Bedford/St. Martin’s in 2015.