The Writing Center – Valle Verde
Comma Rules and Commonly Used Commas
Commas are important punctuation in academic writing because they show the reader where
to pause to understand necessary information. Commas act as breaks, introductions, and lists
for the information. Where a comma tells a reader where to pause before additional
information, a period tells a reader to expect new information to follow in a different sentence.
Using Commas with Coordinating Conjunctions

Coordinating conjunctions are the words used to merge two or more independent
clauses (or complete sentences) together. There are seven coordinating conjunctions
in English, and they are referred to as FANBOYS.
For, And, Nor, But, Or, Yet, So

Whenever two independent clauses are joined with coordinating conjunction, a writer
needs a comma for the reader to know they are two separate sentences. These are
known as compound sentences.
Example 1: Mark slept in, so he was late to class.
Example 2: You can either stay home, or you can go to the movies.

When the two complete ideas and their verbs are joined by the same subject, a
comma is NOT necessary before the coordinating conjunction.
Example 1: Mark slept in and was late to class.
Example 2: You can either stay home or go to the movies.

In Sentence 1, the verbs “slept” and “was” both belong to Mark, so a comma is not
needed. The same goes for Sentence 2 because the complete thoughts “stay home”
and “go to the movies” both refer to “You can.”
Using Commas with Introductory Phrases

Introductory phrases are used to include information about the five Ws (who, what,
when, where, why) or the how of the independent clause. Introductory phrases often
start with prepositions or participles, which include a variety of verb phrases (see
below).
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
A more complete list of starting words for introductory phrases can be found in B3-e,
page 325, of Hacker’s A Writer’s Reference. These are known as complex sentences.
Prepositional Phrase: Around the beginning of summer, the parks get very packed with parties.
Before leaving for work, the parents finish getting the children ready for
school.
Because the cat got out of the house, the neighbors missed their flight
chasing it down.
Participial Phrase:
Jumping up and down, the toddler threw a tantrum.
Exhausted from the sun, we left the zoo thirsty and sleepy.
Using Commas in Run-On Sentences

For more information on run-on, or fused, sentences, see the Run-Ons and Comma
Splices handout provided by the Valle Verde Writing Center or review section G6 in
Hacker’s A Writer’s Reference.
Keeping the Subject with its Verb

The subject, or noun, of the sentence and the verb, or action, can NEVER be separated
within the sentence by punctuation like open-ended commas. Error and correction
examples of open-ended and close-ended commas are listed below.
Error 1: Edgar Allan Poe, who wrote many stories about death died young.
Correction 1: Edgar Allan Poe, who wrote many stories about death, died young.

Because there are two commas around the appositive, or descriptive phrase, the
subject “Edgar Allan Poe” and the verb “died” are not divided.
Using Commas in Lists and Series

When writing lists that come after the words “like” or “such as,” a writer does not
need a comma before the introductory words. However, a writer will use commas to
separate the items in the list or series.
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Example 1:
Many cars such as Corolla, Camry, and Tundra are made by Toyota.
Example 2:
Doug participates in almost every sport like football, basketball, and hockey.
Example 3:
When students focus too much on work, family, and extra-curricular activities,
they forget to spend time on school.
Using Commas with Quotations

When directly quoting a person or story, commas tell the reader when the quote is
beginning and ending. Quoting other people follows the same formatting whether the
essay is a third person research paper or a first person narrative.
Example 1:
Example 2:
Example 3:
According to Dr. Brown, “History is an intricate aspect of human culture.”
The leading scientist on the case said, “The results were inconclusive with our
hypotheses,” which means they need to keep experimenting.
“Your uncle passed away,” my mom said when I came home.
Some information courtesy of:
Hacker, Diana and Nancy Sommers. A Writer’s Reference. Boston: Bedford St. Martins, 2011. Print.
Johnston, Ted and Joe Old. English Beyond the Basics. El Paso: High Sun Publishing, 2014. Print.