A handout from the Online Information Series
Copyright (c) 2002, Jolene M. Morris, All Rights Reserved

25 Comma Usage Rules

(Common usage rules plus APA Manual, pp. 78-80)

Rules are printed in green text. Examples are in blue.

Use a comma to separate two independent sentences combined with a conjunction.

Jolene finished the race, but George didn't.

Use a semi-colon between the two independent sentences combined without a conjunction.

Jolene finished the race; George didn't.

If the conjunction is "so" and is followed by "that," this is an exception to rule #1. The word "that" makes the second sentence subordinate.

Jolene finished the race so that she could eat the lunch.

Do not use a comma to separate a sentence with only a compound subject or compound verb.

Jolene finished the race and the lunch.
Jolene and George finished the race.

Use a comma in place of "that."

The good news is, Jolene won the race.

Use a comma after an introductory phrase of more than three words.

In the heated race, Jolene was the winner.

Use a comma after an introductory phrase of three words or less when clarity or emphasis is needed.

As she ate, Jolene relaxed from the race.

Do not use a comma when the introductory phrase follows the main clause.

Jolene is sure to win the race if she enters it.

Use a comma to set off an introductory phrase that separates the subject from the verb regardless of the number of words in the phrase.

Jolene, in order to win the race, ran as fast as she could.

Use a comma in a series of more than two items. A comma before the conjunction is required in APA papers.

Jolene ran the race, ate the lunch, and went home.

Use a semicolon in a series of more than two items when a comma appears elsewhere in the list.

Jolene ran the race; ate the lunch of a hamburger, Coke, and fries; and went home.

Do not use a comma in a series of only two items.

Jolene ran the race and ate the lunch.

Do not use a comma if extra words added to a sentence are needed to clarify.

Jolene and George went home each to his or her separate home.

Use a comma if extra words added to a sentence aren't needed but add extraneous information only.

Jolene and George went home, each driving separate cars.

Use a comma to identify an appositive (unnecessary clarification of a noun).

The race winner, Jolene, ate the lunch. ("Jolene" is not needed because there was only one race winner.)

Do not use a comma to identify an appositive (if the appositive is necessary to clarify which one).

The race finisher Jolene ate the lunch. ("Jolene" is needed to clarify which race finisher.)

Use a comma to offset an embedded expression.

He was, I used to think, a slob.

Use a semi-colon and a comma to offset a conjunction (conjunctive adverb) of more than one syllable.

Jolene won the race; furthermore, she ate the lunch.

Use a comma to offset a person being addressed (being spoken to).

Jolene, I'm pleased you won the race.

Use a comma to offset a sentence beginning with "Yes," "No," or any exclamation.

Oh, Jolene won the race.

Use a comma to offset conjunctive adverbs.

Obviously, Jolene won the race.

Do not use a comma with composite adjectives/modifiers--when each modifier modifies the one after it, and only the final modifier modifies the noun.)

Jolene was a very tired racer. (The racer is very tired. It makes no sense to say that she is a "very racer.")

Use a comma with parallel adjectives. (All adjectives modify the noun.)

Jolene was a tired, happy racer. (The racer is tired, and the racer is happy.)

Use a comma before examples introduced by "especially" or "such as."

Jolene likes races, especially that race.

Use a comma to represent words or phrases omitted in a sentence.

Jolene likes green; George, blue.

Use a comma to offset adjectives that follow the noun they modify.

The old car, rusted and noisy, went down the road.

Use a comma to offset a confirmatory question.

Jolene finished the race, didn't she?

Use a comma to offset phrases of contrast and additional phrases when used parenthetically.

The car was red, not blue.

Use a comma to offset a direct quote from the tag.

Jolene said, "I am hungry."

Use a comma on the rare occasions when two of the same verb are together in a sentence.

Where you now are, are you happy?

Use a comma when a verb phrase is at the end of a sentence.

Jolene and George ate lunch, each hoping to relax.

Use a comma in a direct quote when it is in conjunction with parenthesis, brackets, ellipses, quotations, or periods after an abbreviation.

"I won the race at 6 p.m.," Jolene said.

Do not use a comma in a direct quote when it is in conjunction with a semi-colon, a colon, a dash, an exclamation point, or a question mark.

"I won the race!" Jolene exclaimed.

Use a comma in dates when the day of the date is given.

I remember July 5, 2001, very well.

Do not use a comma in dates when only a month and year are given.

I remember July 2001 very well.

Use a comma to separate elements of addresses or dates after the first element.

George lives at 1234 Main Street, Denver.

But do not use a comma in addresses or dates if the elements are already separated by a preposition.

George lives at 1234 Main Street in Denver.

Use a comma following the salutation of a friendly letter. Use a comma following the complimentary close of any letter.

Dear Jolene,
Sincerely yours,

Use a comma to separate groups of three digits in most numbers of 1,000 or more.

Jolene won the prize money of $15,000.