Rules for Comma Usage
1. Use commas to separate items in a series (up to the conjunction).
To have a series of items, one must have at least three. A conjunction
(coordinating conjunction) is one of seven words used to connect
words, phrases, or sentences. These words are and, but, or, nor, for
(meaning because), so, and yet (meaning but).
I must mow the lawn, trim the hedges, and plant the flowers.
2. Use a comma to separate two adjectives preceding the noun they
An adjective is used only to describe a noun or pronoun.
I have always dreamed of owning a beautiful, sleek horse.
3. Use a comma before a coordinating conjunction when it separates two
independent clauses.
First of all, independent clause is a fancy word for complete sentence,
or a clause that can stand alone. Coordinating conjunctions were
covered in rule number 1, so all this rule means is that if you put two
complete sentences together and join them with a coordinating
conjunction, then you must use a comma before the conjunction. If
the second half of the statement does not express a complete thought,
then you do not use a comma.
You have started research class, and you will be having a
wonderful time!
You have started research class and will be having a wonderful
4. Use a comma after an interjection or other short introductory element.
An interjection is a word that shows emotion. If it is excessive
emotion, it will be followed by an exclamation point. If a mild
emotion, it will be followed by a comma.
Hey, what is for dinner tonight?
Man, I forgot my cellular phone.
Usually, I watch Fear Factor on Monday evenings.
5. Use a comma after an introductory participial phrase.
A participle is an action adjective. In other words, it is a word that
shows action but does not function as the verb in a given sentence. A
participle is only one word. A participial phrase is a participle plus
any accompanying thoughts. A participial phrase will begin with a
participle. The entire phrase, led by the participle, will act as an
adjective. When such a phrase introduces the sentence, it is followed
by a comma.
Participle: That is a drinking fountain.
Participial phrase:
his mind.
My father, gathering his courage, spoke
Introductory participial phrase:
father spoke.
Gathering his courage, my
6. Use commas to set off a nonessential participial phrase.
Even when the participial phrase does not occur at the beginning, it
may still require commas. If it is considered nonessential, it should be
set apart with commas. It should be considered nonessential if it
contains information that is not crucial for the identification of the
noun or the comprehension of the base sentence.
My niece, attending graduate school, loves chocolate sodas!
Dr. Huff, walking to Frith, dropped her Diet Coke.
7. Use a comma after two or more introductory prepositional phrases.
A prepositional phrase contains a preposition (first word), possibly an
adjective or adverb, and then a noun or pronoun (required, last word).
The noun/pronoun at the end of a prepositional phrase is called the
object of the preposition. A prepositional phrase may contain as few
as two words, or it may contain several.
List of common prepositions: about, above, across, after, against,
along, among, around, at, before, behind, below, beneath, beside,
between, beyond, but, by despite, down, during, except, for, from, in,
inside, into, like, near, of, off, on, onto, out, outside, over, past, since,
through, throughout, till, to, toward, under, underneath, until, up,
upon, with, within, without.
Prepositional phrase: The child is playing in the yard.
Introductory prep. phrase:
beautiful trees.
In the country one can see
Introductory prep. phrases:
trees are tall.
At my home in the country, the
*Prepositions are not used alone. You should never end a sentence or
phrase with a preposition by itself.
8. Use a comma after an introductory adverb clause.
Clauses are either independent or dependent. Independent clauses are
complete sentences that stand alone. Dependent clauses cannot stand
alone. An adverb clause is dependent. A clause, by definition, also
contains a subject and verb. That is why some people punctuate
clauses as sentences. An adverb clause begins with a subordinating
conjunction, a word which, in itself, carries meaning. That is
followed by a subject, verb, etc., and the entire clause functions as an
adverb does, telling how, when, or under what conditions something
is done. If an adverb clause begins your sentence, you follow it with a
List of common subordinating conjunctions: as, after, although, as,
as if, as long as, as soon as, as though, because, before, being that,
considering that, if, in case, in order that, inasmuch as, insofar as, just
so, lest, since, though, unless, until, when, whenever, whereas,
wherever, whether, while.
Introductory Adverb Clause: Because you are so curious, I will
buy you a book.
9. Do not use a comma in front of an adverb clause that follows an
independent clause.
This is really just the reverse of rule #7.
I will buy you a book because you are so curious.
10.Use a comma to set off an appositive of more than one word.
An appositive is a noun that renames a nearby noun (usually right in
front of it). The only parts of speech that can be between the first
noun and the second are adjectives and adverbs.
My best friend, a cashier at Wal-Mart, is always very positive and
happy. (cashier is the appositive renaming the noun friend).
I just finished one of my favorite novels, The Giver.
My sister Emily works for Dr. Donovan. (No comma is necessary
because the appositive Emily is a one-word appositive renaming
11.Use commas to set off nouns used in direct address.
To directly address means to speak to the noun. Rather than speaking
about your friend Tom, you directly address him.
Tom, I like your new car!
I think, Tom, that you should study more.
I really like that house, Tom.
12. Use commas to set parenthetical expressions apart from the
A parenthetical expression is inserted into the flow of
thought. It may be in the middle of a sentence or between sentences,
but it does
not deal directly with the topic at hand. They are like intellectual
Common parenthetical expressions: of course, if possible, actually,
nevertheless, in fact, by the way.
I think, in fact, that a picnic would be ideal for the celebration!
Timothy, naturally, should be the one to carve the turkey.
13. Use a comma after a name followed by an abbreviation, such as Jr.,
Sr., or M.D.
I just met Larry Edwards, Jr.
14.Use commas to set apart a nonessential adjective clause.
An adjective clause is another type of dependent clause. It cannot
stand alone. Unlike an adverb clause, however, that begins with a
subordinate conjunction and describes how, why, or under what
conditions, an adjective clause begins with a relative pronoun, follows
a noun, and acts as an adjective describing that noun. If you believe
the clause is necessary to the identification of the noun, then it is
considered essential and requires no commas. If, however, you do not
consider it essential to the understanding and identification of the
noun it describes, then it is considered nonessential and requires
Relative Pronouns: who, whom, whose, which, that
Essential: The girl who is wearing the red jacket is in third grade.
Nonessential: Tonia, who is wearing the red jacket, is in third
*Use who to begin the clause if it serves as the subject or predicate
nominative of the clause; use whom if it serves as the direct object,
indirect object, or object of the preposition.*