Basic Comma Rules

1. Use commas to separate three or more words or phrases in a series.

Examples:

        The colors of the flag are red, white, and blue.

        I scraped, sanded, and varnished the old chair.

        They had money, peace of mind, and even good grammar.

The exception to this is when the items in the list include commas already, such as the names of cities and states. In that case, use semicolons to separate the items in the list.

Example:        

I have lived in Birmingham, Alabama; Atlanta, Georgia; Nashville, Tennessee; and Richmond, Virginia.

2. Use commas to indicate that a person is being addressed by name.

Examples:

        Fred, did you take the pizza?

        Did you take the pizza, Fred?

3. Use commas after phrases, clauses, or small words that introduce the main idea of your sentence. Included in this group are transition words and phrases such as "however," "nevertheless," "on the other hand," etc.

Examples:

        No, Fred did not take the pizza.

Because Kathy went to the Writing Lab often, she learned to correct all of her  grammatical errors.

        After the movie, we all went home.

        Consequently, Kathy was glad that she went to the Writing Lab.

If one of those transitions words or phrases is in the middle of a sentence, separating two independent clauses, use a semicolon in front of it and a comma after.

Example: Mr. Svab is sometimes funny; however, he is horrifyingly ugly.

4. Use commas to set off words, phrases or clauses that comment on or give additional information about the main part of the sentence, or otherwise interrupt the natural flow of the sentence.

Interrupters are also called appositives or non-restrictive elements.

Examples:         Chicago, the windy city, is my home town.

        Joe, after visiting the Smiths, became a vegetarian.

        Priscilla, in the meantime, went skiing.

        Everyone did not, as a result, go windsurfing.

5. Use commas before coordinating conjunctions such as "and," "or,", "but" that join two complete sentences/independent clauses, or when the comma is needed for clarity, emphasis, or contrast.

Examples:

        Chicago may be windy, but it's home.

        Joe went to the Writing Lab several times, and he is writing better essays as a result.

If the second half of the sentence is a dependent clause, with no subject, a comma is not needed.

Example: I love the taste of pineapple but abhor Hawaiian pizza.

6. Use a comma before non-essential, modifying elements that follow the words and main clause and provide information that supplements or comments on the basic meaning of the main clause.

Examples:

        I live in New Mexico, the "land of enchantment."

        Many college students struggle to pay tuition costs, which are steadily increasing.

7. Use a comma between coordinate adjectives not joined by "and." Coordinate adjectives each modify the noun independently.

Example:

        The hiker traveled along the steep, narrow trail.

In the above sentence, both "steep" and "narrow" modify "trail." Thus they are coordinate adjectives. Do not use a comma between adjectives that are not coordinate—that do not both modify the same noun.

Example:

        The team members all wore lime green jackets.

In the above sentence, "lime" modifies "green," not "jackets."

If two adjectives can have “and” put between them, and the sentence still makes sense, then use a comma.

Example: The white, black, and brown dairy cow is tired.

8. Use a comma when noting dates and addresses.

Example:

        It was on April 16, 1963 that Martin Luther King, Jr., wrote his famous letter.

        Veggie-matics can be ordered from Cheapstuff Inc., 10000 First Avenue N.E., New York, New York 10070.