Using Commas

        The comma is a valuable, useful tool in a sentence because it helps the reader pause in the right places. The rules provided here are those found in traditional handbooks: however, in certain rhetorical contexts and for specific purposes, these rules may be broken.

1. Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions:

AND, BUT, FOR, OR, NOR, SO, YET

The game was over (,) but the crowd refused to leave.

2. Use commas after introductory (a) clauses, (b) phrases, or (c) words that come BEFORE the main clause.

Because her alarm clock was broken, she was late for class.

If you are ill, you ought to see a doctor.

Clues:

(a) Some common starter words for clauses are:

AFTER, ALTHOUGH, AS, BECAUSE, IF, SINCE, WHEN, WHILE

(While I was eating, the cat scratched at the door.)

(b) Some common starter words for phrases are:

VERB + ING

(Having finished the test, he left the room.)

TO + VERB

(To get a seat, you'd better come early.)

LONG PREPOSITIONAL PHRASE (over four words)

(After the test but before lunch, I went jogging.)

(c) Some common words preceding a comma:

YES, HOWEVER, WELL

(Well, perhaps he meant no harm.)

3. Use a pair of commas in the middle of the sentence to set off phrases, clauses, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.

Clues:

Can you leave out the clause, phrase, or word and still have the sentence make sense?

Does the non-essential clause, phrase, or word interrupt the flow of words in the original sentence?

Can you move the non-essential element around in the sentence?

4. Does the clause begin with "THAT"? "THAT" clauses after nouns are almost always essential. "THAT" clauses which follow a verb expressing mental action are always essential. No comma is needed in these cases.

"THAT" after nouns:

(The book that I borrowed from you is excellent.)
(Apples that are green are usually called Granny Smith apples.)

"THAT" clauses which follow a verb expressing mental action:

(She believes that she will be able to earn an A.)
(He dreams that he can fly.)
(I contend that it was wrong to mislead her.)
(They wish that warm weather would finally arrive.)

ESSENTIAL: (no comma)

A student who cheats only harms himself.

The girl wearing the tight sweater is attracting a lot of attention.

NON-ESSENTIAL: (A pair of commas)

Apples, which are my favorite fruit, are usually harvested in autumn.

Fred, who often cheats, is just harming himself.

Professor Benson, grinning from ear to ear, announced that the exam will be tomorrow.

Tom, the captain of the team, was injured in the game.

It is up to you, Jane, to finish.

She was, however, too tired to make the trip.

Two hundred dollars, I think, is sufficient.

5. Use commas to separate three or more words, phrases, and clauses written in a series.

Clue: Are the last two items in the series connected with either AND or OR?

(She couldn't choose between John, Jim, or Joe.)
(The candidate promised to lower taxes, solve the energy shortage, and end unemployment.)

6. Use commas to separate two or more coordinate adjectives that describe the same noun.

Clues:

Can the adjectives be written in reverse order? (If your answer is yes, add a comma.)

Can you add an AND between the adjectives? (If your answer is yes, add a comma.)

(a greedy, stubborn child)
(a white frame house)
(a purple wool shawl)
(an easy, happy smile)

7. Use commas near the end of the sentence to separate sharply contrasted coordinate elements in the sentence or to indicate a distinct voice pause.

(He was merely ignorant, not stupid.)
(You're one of the senator's right-hand men, aren't you?)

8. Use commas to set off middle phrases at the end of the sentence which refer back to the beginning or middle of the sentence. These phrases are free modifiers which can appropriately be placed at the beginning, middle, or end of the sentence without causing confusion for the reader.

CORRECT: Nancy waved enthusiastically at her parents on the boat, laughing gaily in the process.

INCORRECT: Jane waved at Nancy, laughing gaily. (Who is laughing, Jane or Nancy?)

9. Use commas to set off all geographical names, items in dates (except the months and day), addresses (except the street and number), and titles in names.

(Birmingham, Alabama, gets its name from Birmingham, England.)
(July 22, 1959, was a momentus day in his life.)
(Who lives at 1600 Pennsylvania Avenue, Washington, D.C.?)
(Donald B. Lake, M.D., will be the principal speaker.)

10. Use commas after "he said," etc. to set off direct quotations and after the first part of a quotation in a sentence.

(John said, "I'll see you tomorrow.")
("I was able," she answered, "to complete the assignment.")

11. Use commas anywhere in the sentence to prevent possible confusion or misreading.

(To John, Harrison had been a sort of idol.)

Comma Abuse

Commas in the wrong places can chop ideas into wrong pieces or confuse the reader with unnecessary pauses.

Don't separate a subject from its verb.

The eighteen-year old in California, is now considered an adult. (INCORRECT)

The most important attribute of a ball player, is quick reflex actions. (INCORRECT)

Don't put a comma between 2 verbs!

We laid out our music and snacks, and began to study. (INCORRECT)

I turned the corner, and ran smack into a patrol car. (INCORRECT)

Don't put a comma before a dependent (or subordinate) clause when it comes after the main clause (except for extreme contrast.)

She was late for class, because her alarm clock was broken. (INCORRECT)

You ought to see a doctor, if you are ill. (INCORRECT)

(BUT, what happens if the order of the clauses in these sentences is reversed? See number 2 above.

She was still quite upset, although she won the Oscar. (CORRECT - EXTREME CONTRAST)

Thanks to the OWL On-Line Writing Lab at Purdue University.