Grammar Rules


English Punctuation: How to Use Commas Correctly

Commas are used to separate a sentence’s elements, to connect independent clauses, to avoid confusion, and much more. Here, we offer a brief, basic guide to using commas correctly.

Using Commas to Separate a Sentence’s Elements

Commas provide clarity, particularly in sentences that contain several different elements.
  • Always use commas to separate the elements of a series of three or more things, particularly the last two. “She saddled her horse, hopped on, and rode off into the sunset.”
  • You may have learned that it’s not necessary to use a comma before “and” – and that’s fine in most cases. However, there are some times when adding a comma before “and” can help to prevent confusion, particularly when a series of words includes terms that have a tendency to glom together (like spaghetti and meatballs). “He went to the grocery store, where he bought cheese, spaghetti, and meatballs.”

How to use Commas and Conjunctions to Connect Independent Clauses

Conjunctions are words such as and, for, nor, but, yet, and so.
  • Use a comma after a conjunction to provide balance. “We drove to the beach, but we left since the parking lot was full.”
  • One of the most common comma placement errors is the usage of a comma after a conjunction rather than before: “Nancy’s schedule was very busy but, she always made time to go to the gym.”

Using Commas to Set Off a Sentence’s Introductory Element

While it is not always necessary to use a comma after a sentence’s introductory element, it’s usually a good idea to do so since omission can lead to hesitancy or confusion.
  • Notice how the comma in this sentence infuses the words with greater meaning: “While lighting the candles on John’s birthday cake, Susan realized that he would soon be an adult.”
If you are ever in doubt about whether to use a comma after an introductory element, err on the side of caution and insert a comma – it’s never incorrect to do so.

Using Commas to Accentuate Parenthetical Elements

Parenthetical elements, or added information, increase a sentence’s value by providing additional information that isn’t necessary for getting one’s point across, but that is worth stating.
  • In this sentence, the parenthetical element is italicized: “The North River Bridge, which was built in 1902, collapsed on Saturday.”
In the example above, the parenthetical information provides the reader with a sense of context that helps provide insight into the cause of the bridge’s collapse. When writing about locations, such as cities, states, and nations, treat the middle element as parenthetical. For example:
  • We visited Bozeman, Montana, last summer.
  • London, England, is a destination everyone should visit at least once.
When the state or nation takes on a possessive form, the rule no longer applies. For example:
  • Williamsburg, Virginia’s connection with our nation’s history is well-known.
In addition, the second comma is dropped when the location’s name is compounded, as follows:
  • Facebook, as a Boston, Massachusetts-based company, is now known throughout the world.

Using Commas to Frame Quoted Elements

Many writers use quoted material rarely, if ever. Because it’s fairly uncommon to use quotes in everyday writing, this rule can be difficult to remember. If ever in doubt, find a page from an article that incorporates several quotations and uses it as a model for constructing sentences with quotes.
  • “The question is,” said Mary, “why it is possible to make the same words mean many things.”
  • In Lectures in America, Gertrude Stein writes, “A long complicated sentence should force itself upon you.”
As the above examples illustrate, commas generally separate quotes from the remainder of the sentence, which usually introduces or explains the quotation.