Commas
The Brenham Writing Room
Created by D. Herring
Why use a Comma?
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A comma is a punctuation mark that
helps keep distinct ideas separate.
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Commas signal meaning, so it is critical
to use them correctly!
How do I use Commas correctly?
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There are set guidelines for using commas.
You must know and understand the rules of
comma usage.
 In particular, you must know and understand
how to use
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Commas between items in a series
Commas after introductory word groups
Commas around appositives and interrupters
Commas in compound sentences
Commas in complex sentences
1. Using Commas between Items in
a Series

When you have a list of three or more items in
a series, you must include a comma between
each item. With the last item, the comma will
come before the “and/or.”

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We ate fish, shrimp, and oysters.
She wants to be a teacher, librarian, or counselor.
Do not include a comma when you have only
two items in the series.
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We ate fish and shrimp.
She wants to be a teacher or librarian.
2. Using Commas after Introductory
Word Groups

Use a comma after an introductory word,
phrase, or clause to let your reader know
when the main part of the sentence is
starting.
However, it’s only the fifth week of the
semester. (introductory word)
 According to my teacher, I am doing well in
my math course. (introductory phrase)
 Because I didn’t study for the exam, I didn’t
pass. (introductory clause)
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3. Using Commas with Appositives
& Interrupters

What is an appositive?
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An appositive comes directly after a noun
and renames it.
Ms. Bonnie, our class tutor, really helped me
improve my writing.
 My favorite restaurant, TGI Fridays, just opened
in College Station.
 Ana, one of my 0321 students, won a
scholarship to SHSU.
 My English teacher, Mr. Herring, assigns a lot of
homework.

Appositives & Interrupters cont.
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What is an Interrupter?
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An interrupter is an aside or transition that
interrupts the flow of a sentence but doesn’t
affect its meaning.
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By the way, most of the students did well on the first
writing assignment.
Some of the students, however, did not do well.
Many students, incidentally, received a better grade
because they got help from the tutor.
Others, on the other hand, received lower grades because
they didn’t take time for tutoring.
Appositives & Interrupters cont.
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We use commas around appositives and
interrupters to tell our readers that these
elements provide extra information but are not
essential to the meaning of a sentence.
Wherever these elements fall in the sentence,
they should be offset with commas.
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By the way, most students passed 0320.
Most students, by the way, passed 0320.
Most students passed 0320, by the way.
Appositives & Interrupters cont.
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It is important to understand how a transitional
word is being used so that you can properly
punctuate.
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I did well on my math test; however, I did not do
well on my English test. (transitional word as
introductory element)
I did well on my math test; I did not, however, do
well on my English test. (transitional word as
interrupter)
I did well on my math test, however, I did not do
well on my English test. (incorrect use—creates a
comma splice!)
Appositives & Interrupters cont.
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Sometimes an appositive is essential to the
meaning of the sentence. When the meaning
of the sentence would not be the same without
the appositive, it should not be offset with
commas.
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The actor John Travolta has never won an
Academy Award.
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The actor has never won an Academy Award.
The clothing store Foleys has been bought out by
another company.
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The clothing store has been bought out by another
company.
4. Using Commas in Compound
Sentences
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When you have a compound sentence—
two independent clauses joined together
with a coordinating conjunction—you
must use a comma before the
coordinating conjunction.
We went out to dinner, and then we went to
see a movie.
 We wanted to go out to dinner, but we didn’t
feel like going to the movies afterwards.
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Compound Sentence continued
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If you have a coordinating conjunction
joining two clauses, but one is
independent and the other is not, no
comma is needed!
We went out to dinner and then to see a
movie.
 We wanted to go out to dinner but not to the
movies.
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5. Using Commas in Complex
Sentences
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Complex sentences join an independent
clause with a dependent clause or
relative clause.
A dependent clause begins with a
subordinating conjunction (dependent word)
and cannot stand alone.
 A relative clause begins with a relative
pronoun (who, which, that) and cannot
stand alone.
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Commas with Dependent Clauses
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When a dependent clause is used as an
introductory clause, it is followed by a comma.
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Because I didn’t study for the exam, I didn’t pass.
When you get to work, give me a call.
However, when a dependent clause comes at
the end of the sentence, it is generally not
preceded by a comma.
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I didn’t pass because I didn’t study for the exam.
Give me a call when you get to work.
Commas with Relative Clauses
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If a relative clause can be taken out of
the sentence without changing the
meaning, then it should be offset with
commas.
My dog, who is a Beagle, barks too much.
 My laptop, which weighs only five pounds,
fits into my backpack.
 My history teacher, who is about a hundred
years old, just doesn’t understand me.
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Relative Clauses continued
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If a relative clause cannot be taken out of
the sentence without changing the
meaning, then it should not be offset with
commas.
The man who stole my purse has been
arrested.
 The shirt that I bought yesterday already
has a tear in it.
 The English class that I’m taking in the fall
meets on Tuesdays and Thursdays.
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Relative Clauses continued
REVIEW:
 When should I use that?
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When should I use which?
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That is used to introduce a restrictive (essential)
clause describing an animal or a thing.
Which is used to introduce a nonrestrictive (nonessential) clause describing an animal or a thing.
When should I use who?
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Who is used to introduce both a restrictive and
nonrestrictive clause describing an animal or a
person.
Relative Clauses continued
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Incorrect: The man that stole my purse has been
arrested.
Correct: The man who stole my purse has been
arrested.
Incorrect: The English course which I’m taking this fall
meets on TR.
Correct: The English course that I’m taking this fall
meets on TR.
Incorrect: My laptop, that weighs five pounds, fits into
my backpack.
Correct: My laptop, which weighs five pounds, fits
into my backpack.