Commas

Definition

When two or more independent clauses are joined by a coordinating conjunction, you need a comma before the conjunction.

An independent clause is a complete sentence that can stand on its own because it is made of a subject (noun or noun phrase) and predicate (verb or verb phrase), such as “I walk.” 

A coordinating conjunction is a linking word that connects two independent clauses together. (There are only seven coordinating conjunctions, so they are easy to memorize with the acronym FANBOYS, which stands for the conjunctions for, and, nor, but, or, yet, and so.)

Examples

Yes: My family lives in a blue house, and my neighbors live in a white house.
(The comma separates two independent clauses that are joined by the coordinating conjunction “and.”)

Yes: Sue’s parents told Sue to be home by midnight but knew she would be late.
(The second clause is not independent so a comma is not used.)

No: Sue’s parents told Sue to be home by midnight but she was fifteen minutes late.
(A comma is missing before the coordinating conjunction “but” that separates the two independent clauses.)

Review

Other

• If the two independent clauses are very short and closely connected, the comma becomes optional.
  
  • Yes: Raise your right hand, and repeat after me.
  • Better: Raise your right hand and repeat after me.