The 8 basic rules of the comma

1. Punctuation Basics:
The Rules of the Comma

2. Rules of Comma Usage
There are specific rules for using the
comma, but keep in mind the following:
• The comma is never inserted into a sentence where
you believe you would “take a breath;” after all, do
you really read everything you write aloud?
• The comma is never inserted into a sentence where
you can use a period; if you do, you create a comma
splice.

3. 8 Most Common Rules
1. To separate main clauses linked by a
coordinating conjunction
2. To set off introductory elements
3. To set off non-essential or parenthetical
elements
4. To separate elements in a series
n To separate coordinate adjectives
n To set off quoted elements
n To avoid confusion
n Typographical reasons

4. RULE #1: To separate main clauses linked by a
coordinating conjunction (and, but, for, nor, yet, or, so,
although)
I enjoy sending email, so I seldom write by hand anymore.
I enjoy sending email, yet I rarely have the time to write it.
I enjoy sending email, but prefer surfing the internet.
Note that what comes before the comma is a
complete sentence and what comes after the
comma and coordinating conjunction is also a
complete sentence.
An excellent approach to learning this rule is to
memorize the 8 coordinating conjunctions listed
above.

5. RULE #1: To separate main clauses linked by a
coordinating conjunction
If the coordinating conjunction is not linking
main clauses, then a comma is not
necessary.
Email is fast but impersonal.
Never follow the coordinating conjunction
with a comma, even if you would pause
there when speaking.

6. RULE #2: To set off introductory elements
Natural word order in English prefers the subject of
the sentence to be stated first, followed
immediately by the main verb; if we move an
element that typically follows the main verb to
beginning of the sentence, then a comma should
come immediately after that element.
When first created, the internet was used only by the military.
Over the years, more and more people are using the internet.

7. When not to use a comma after an
introductory element
There are also introductory words and phrases
(however, therefore, in conclusion, etc.) that
require a comma to follow.
However, the NSF has made the internet widely available.
If the introductory element is extremely brief (i.e. a
single, one-syllable word), then the comma,
although correct, may be omitted.
Now most Americans have internet access.

8. RULE #3: To set off non-essential or
parenthetical elements
The internet, which was invented by the military, is a powerful
research tool.
Her new computer, an IBM laptop, is much faster than her old one.
The internet service is, of course, an added expense.
Note that 2 commas are always used, never just one.
If the element is essential to an understanding of the
sentence, then no commas are used.
The web designer who works for our competitor uses professional
software.

9. Understanding the difference between
essential and non-essential phrases
In order to determine whether a phrase is essential or not
to the sentence, you must consider context.
My brother, who is a teacher, lives in Lexington.
My brother who is a teacher lives in Lexington.
Why the difference? In the first sentence, I only have one
brother, so the fact he teaches is extra (or non-
essential) information; in the second sentence, I must
have more than one brother, so the fact he teaches
(and does not drive a bus) is essential to understand
the sentence.

10. RULE #4: To separate elements (more than
2) in a series
The internet is fast, efficient, and addictive.
The internet is fast, efficient, but addictive.
If you were taught the alternative rule of omitting the
comma before “and,” that is fine. Just be
consistent in your writing.
The internet is fast, efficient and addictive.

11. RULE #5: To separate coordinate
adjectives
The designer created an effective, dynamic webpage.
If you can rewrite the sentence with an “and” (or “but”)
between the adjectives, then a comma is needed.
The designer created an effective and dynamic webpage.
If no “and” or “but” is possible, then a comma is
unlikely to be needed.
The webpage designer is a little old lady.

12. RULE #6: To set off quoted elements
In his article, Johnson states, “cyberspace was becoming the new
final frontier” (6).
Do not use a comma if the quotation is presented as
indirect speech.
In his article, Johnson states that “cyberspace was becoming the
new final frontier” (6).

13. RULE #7: To avoid confusion
Unclear:
Outside the acceptable use policy of the computer classroom is
clearly posted.
Better:
Outside, the acceptable use policy of the computer classroom is
clearly posted.
Best (rewrite the sentence using no commas):
The acceptable use policy of the computer classroom is clearly
posted outside the room.

14. RULE #8: Typographical reasons
Commas divide elements in dates and addresses.
The computer company relocated its main office from Cincinnati,
Ohio, to Northern Kentucky.
The office opened on January 1, 2001, for its first day of business.