Comma Errors

Common rules for comma usage

A. Use a comma before a coordinating conjunction (and, but, or, so, nor, for, and yet) when the conjunction is joining two independent clauses (complete sentences).

For example: "All of us were at the game" is a sentence. "Jack was at the picnic" is also a sentence. These two sentences might be joined by the conjunction "but." Whenever two sentences are joined using a coordinating conjunction, a comma must be placed immediately before the conjunction:

All of us were at the game, but Jack was at the picnic.

NOTE: When conjunctions are used to join two things within a complete sentence, no comma is needed:

Elissa and Mona are in the same English class.
Laura went swimming and spent time on the beach.

B. Use a comma after an introductory phrase or clause (group of words).

Writers often start sentences with a clause or a phrase before the subject and verb are introduced. These groups of words often provide additional information about the action of the sentence. Insert a comma after these types of introductory words.

Although the weather was cool, everyone still enjoyed the baseball game.
Because the messenger was carrying such a large package, he stumbled through the door.
In paintings by modern artists, colors are often very bright.

C. Surround "interrupters" with commas.

Words which "interrupt" the flow of the sentence should be surrounded by commas wherever they occur in the sentence.

In your opinion, what is the best route to take?
What, in your opinion, is the best route to take?
What is the best route to take, in your opinion?

The following are some "interrupters" that are frequently surrounded by commas: additionally, as a result, furthermore, in addition, moreover, in the same way, likewise, similarly, however, nevertheless, in contrast, first, second, third, finally, meanwhile, for example, for instance, indeed, of course, on the other hand, consequently, hence, therefore, thus.

NOTE: When you use one of these words to join two sentences, a semicolon must come before it and a comma must come after it.

All of us were at the game; however, Jack was at the picnic.

D. Set off nonessential elements with commas.

Often writers give additional information about a noun that is not necessary in order to understand what person, place, or thing is being referred to. Place commas around this type of information.

Harper Lee, the author of To Kill a Mockingbird, was born in Alabama.
Alice's Adventure in Wonderland, which was written by Lewis Carroll, has become a classic.
Mary is very happy with her new kitchen, a great addition to the house.

E. Use commas to separate items in a list or series.

Students, teachers, parents, and visitors attended the picnic.
My mother put her feet up, sipped some iced tea, and opened the newspaper.

F. Use commas to separate two or more adjectives that describe the same noun equally.

That is a rough, dangerous road.
He dove into the cold, dark water.

NOTE: Not all adjectives describe the noun equally. When they are not equal, do not use commas to separate them.

The two young men walked into the store.
There is a white frame house on the corner.