Commas
Commas often confuse writers and for good reason! Rules governing comma usage vary depending on where and how the comma is used. Complicating this is the fact that sometimes comma usage is a stylistic rather than a grammatical choice. The following are the most common situations that call for commas and the corresponding rules and tips for comma usage:
Lists
Rule: Use commas to separate three or more items in a list.
Consultants can help you brainstorm, draft, and revise a paper.
However, in some cases, the Oxford comma is useful for avoiding confusion. For example:
I love my parents, Taylor Swift, and Draco Malfoy.
(Clearly a list of three things the author loves)
I love my parents, Taylor Swift and Draco Malfoy.
(Suggests the possibility that the author’s parents are Taylor Swift and Draco Malfoy)
I packed light, bringing only my knife, my gun.
Coordinating Conjunctions
Rule: Use commas when joining two independent clauses (complete sentences) with a coordinating conjunction (also known as FANBOYS: For, And, Nor, But, Or, Yet, So.)
Leslie knew she was in trouble, but she didn’t want to admit it.
Tom was worried about his assignment, so he made an appointment at the writing center.
Dialogue and Direct Quotations
Rule: When dialogue or a direct quotation is at the beginning of a sentence, use a comma before the closing quotation marks.
“All this happened, more or less,” writes Kurt Vonnegut at the beginning of Slaughterhouse-Five.
Rule: When the word right before a quote is a verb indicating who said or wrote it, use a comma to introduce the quotation.
At the beginning of Slaughterhouse-Five, Kurt Vonnegut claims, “All this happened, more or less.”
“Look out!” she shouted.
In one of Shakespeare’s most famous soliloquies, Juliet asks, “What’s in a name?”
Introductory Words and Phrases
Rule: Use a comma to separate an introductory phrase or dependent clause from the main part of a sentence.
During the hottest weeks of the summer, everyone left the city.
Meanwhile, Congress was fighting over where to put the capitol.
First the bill has to pass in the House of Representatives.
After dinner they went back to her place.
Everyone left the city during the hottest weeks of the summer.
Adding Information
Rule: Enclose non-essential descriptors in commas.
All kinds of students, including experienced writers, can benefit from the Writing Center.
The Revolutionary War hero Philip Schuyler had three daughters.
(“Philip Schuyler” specifies which war hero and is therefore essential information.)
The eldest sister, Angelica, was the most outgoing.
(There can only be one eldest sister in a family, so her name is non-essential information.)
Sometimes, whether the comma is necessary or not depends on contextual information.
Angelica’s sister Eliza married Alexander Hamilton.
(Angelica Schuyler had two younger sisters, so Eliza’s name is essential information.)
Philip’s daughters – Peggy, Angelica, and Eliza – were all powerful in their own ways.
Adapted from the UMN CLA Center for Writing - Commas