This is another commonly used punctuation mark. There are several instances where you might use a comma.
Use the comma when denoting an appositive, or a break within a sentence that supplements and adds information to the subject.
Bill Gates, CEO of Microsoft, is the developer of the operating system known as Windows.
Use the comma when denoting a series. This is a set of three or more "list" items within a sentence. Many writers omit the last comma as "and" is also a connective ("The basket contained apples, bananas and oranges.").
The fruit basket contained apples, bananas, and oranges.
The computer store was filled with video games, computer hardware and other electronic paraphernalia.
Use a comma if your subject has two or more adjectives describing it. This is somewhat similar to a series, except that it is incorrect to place a comma after the final adjective.
CORRECT - The powerful, resonating sound caught our attention.
INCORRECT - The powerful, resonating, sound caught our attention.
Use a comma when referring to a city and state. It is also necessary to use a comma to separate the city and state from the rest of the sentence.
I am originally from Ventnor, NJ.
Los Angeles, CA, is one of the largest cities in the United States.
Use a comma to separate an introductory phrase (which is usually one or more prepositional phrases) from the rest of the sentence. An introductory phrase briefly introduces the sentence, but is not part of the sentence's subject or predicate, and it therefore should be separated from the main clause by a comma.
After the show, John and I went out to dinner.
On the back of my couch, my cat's claws have slowly been carving a large hole.
Use the comma to separate two independent clauses. Having two independent clauses in a sentence simply means that you can split the sentence into two. If your sentence contains two independent clauses that are separated by a conjunction (such as and , as , but , for , nor , so , or yet ), place a comma before the conjunction.
Ryan went to the beach yesterday, but he forgot his sunscreen.
Water bills usually rise during the summer, as people are thirstier during hot and humid days.
Use a comma when making a direct address. When calling one's attention by name, separate the person's name and the rest of the statement with a comma. Note that this kind of comma is used rarely in writing, because this is something that we do normally while speaking.
Amber, could you come here for a moment?
Use a comma to separate direct quotations. A comma should come after the last word before a quotation that is being introduced . It is not necessary to use a comma in an indirect quote. A comma is usually not necessary if you are not quoting an entire statement.
While I was at his house, John asked me if I wanted anything to eat.
An indirect quotation that does not require a comma.
While I was at his house, John asked, "Do you want anything to eat?"
A direct quotation.
According to the client, the lawyer was "lazy and incompetent."
A partial direct quotation that does not require a comma.