Punctuation

Comma before a coordinating conjunction

When a coordinating conjunction connects two or more independent clauses a comma must precede it. A comma tells readers that one independent clause has come to a close and that another is about to begin.

Example sentence with editing. Original sentence: The city began to lay off nonessential workers and it also cut its summer jobs program for high school students. Revised sentence: The city began to lay off nonessential workers, and it also cut its summer jobs program for high school students.

Example sentence with editing. Original sentence: Nearly everyone has heard of love at first sight but I fell in love at first dance. Revised sentence: Nearly everyone has heard of love at first sight, but I fell in love at first dance.

EXCEPTION:If the two independent clauses are short and there is no danger of misreading, the comma may be omitted.

Example sentence: The plane took off and we were on our way.

TIP:As a rule, do not use a comma to separate coordinate word groups that are not independent clauses.

Example sentence with editing. Original sentence: A good money manager controls expenses, and invests surplus dollars to meet future needs. Revised sentence: A good money manager controls expenses and invests surplus dollars to meet future needs.

The word group following and is not an independent clause; it is the second half of a compound predicate. The two parts of the predicate belong together, so do not separate them with a comma.

Exercises:

Major uses of the comma 1

Major uses of the comma 2

All uses of the comma