Commas

A comma is a punctuation mark that indicates a separation of ideas. They are used in five main ways:

A. To set off a phrase or clause that introduces a sentence:

Ex.: Although he was tired, he wrote his paper.

B. To set off items in a list:

Ex.: The student came in with an assignment sheet, notes, and a rough draft.

Sometimes the comma before the and is left out. Be consistent; use this comma either all of the time or none of the time.

C. To show that explanatory material has been inserted:

Ex.:Mr. Hankins, my instructor, told me to revise my report.

Commas are placed on both sides of the explanatory material to show that the information is not essential; think of them as the parentheses in a math equation.

D. To introduce, set off, or end a direct quotation:

Ex.: "To be or not to be, that is the question," said Hamlet.
        The tutor said, "Your paper is good."
        "Around us are waltzing," said Carl Sagan, "billions and billions of stars."

E. To separate complete sentences joined by a coordinating conjunction:

Ex.: I proved my thesis, so the teacher was happy with my paper.

Common Trouble Areas With Commas

A. A comma is not used before a clause introduced with the word "that."

Ex.: The President and the Congress felt that a balanced budget was possible.

B. A comma is not used to join two complete sentences unless there is a coordinating conjunction; substitute a period or semi-colon.

Ex.: I stayed up all night. I finished my paper.

C. A comma is not used to separate two complete sentences joined by a conjunctive (movable) adverb; substitute a semi-colon.

Ex.: I had enough information; therefore, I didn’t look for any more library materials.