1. Use a comma to separate the elements in a series (three or more things), including the last two.
"She bought an apple, a banana, and some grapes."
"He hit the ball, dropped the bat, and ran to first base."
"He watched T.V., ate chips, and had pop."
2. Use a comma + a little conjunction (and, but, for, nor, yet, or, so) to connect two independent clauses.
"She was invited to the party, but she didn't go."
"He hit the ball well, BUT he ran toward third base."
"He was sick, but he still went to school."
3. Use a comma to set off introductory elements.
"When the cop started to follow him, he realized how fast he was going."
"When he couldn't hit the ball, he noticed he was holding it upside down."
"Running toward third base, he suddenly realized how stupid he looked."
4. Use a comma to set off parenthetical elements.
"Jackie, a girl in my class, laughs to much."
"My sister, who is a year younger than me, still can't beat me in bowling."
"The Founders Bridge, which spans the Connecticut River, is falling down."
5. Use a comma to separate coordinate adjectives.
"I live in a very old, run-down house."
"That tall, distinguished, good looking fellow"
"I have very, crummy shoes."
6 Use a comma to set off quoted elements. Generally, use a comma to separate quoted material from the rest of the sentence that explains or introduces the quotation.
In his article, Woolley states, �cyberspace was becoming the new final frontier�
"The question is," said Alice, "whether you can make words mean so many things."
"Hey," said Bill, "where are you guys going?"
7 Typographical reasons. Commas divide elements in dates and addresses.
The computer company relocated its main office from
Cincinnati, OH, to Northern Kentucky.
The office opened on January 1, 2001, for its first day of business.
Disney World is located in Orlando, Florida.
8 When you begin a sentence with a phrase or dependent clause to introduce a subsequent independent clause, separate the clauses with a comma.
After many years as a criminal prosecutor, she ascended to the bench.
Because the witness was unavailable, the judge allowed the introduction of the testimony pursuant to an exception to the hearsay rule.
I enjoy sending email, so I seldom write by hand anymore.
9 Use a comma to avoid confusion.
For most, the year is already finished.
Outside, the lawn was cluttered with hundreds of broken branches.
Just then, Superman saved the day.
10 5. Do not join independent clauses by a comma.
Stevenson's romances are entertaining, they are full of exciting adventures
It is nearly half past five, we cannot reach town before dark.
It was Monday, I did not do my homework.
Insted, write the above as two sentences each, replacing the commas by periods.
Stevenson's romances are entertaining. They are full of exciting adventures.
It is nearly half past five. We cannot reach town before dark.