To better understand the use of the comma, begin by learning the following eight basic uses. Download or print a PDF of these rules which also include exercises.
Commas (Eight Basic Uses)
1. Use a comma to separate independent clauses
Rule: Use a comma before a coordinating conjunction (and, but, yet, so, or nor, for) when it joins two complete ideas (independent clauses).
- He walked down the street, and then he turned the corner.
- You can go shopping with me, or you can go to a movie alone
2. Use a comma after an introductory clause or phrase
Rule: Use a comma after an introductory clause or phrase. A comma tells readers that the introductory clause or phrase has come to a close and that the main part of the sentence is about to begin.
- When Evan was ready to iron, his cat tripped on the cord.
- Near a small stream at the bottom of the canyon, park rangers discovered a gold mine.
3. Use a comma between all items in a series
Rule: Use a comma to separate each item in a series; a series is a group of three or more items having the same function and form in a sentence.
- We bought apples, peaches, and bananas today. (series of words)
- Mary promised that she would be a good girl, that she would not bite her brother, and that she would not climb onto the television. (series of clauses)
- The instructor looked through his briefcase, through his desk, and around the office for the lost grade book. (series of phrases)
4. Use commas to set off nonrestrictive clauses
Rule: Use commas to enclose clauses not essential to the meaning of a sentence. These nonessential clauses are called nonrestrictive. Clauses which are essential are called restrictive. Both restrictive and nonrestrictive clauses may begin with a relative pronoun (such as who, whom, whose, that, which). A relative pronoun refers to the noun or pronoun that precedes it.
- Steven Strom, whose show you like, will host a party next week. (nonrestrictive)
- John, who spent the last three days fishing, is back on the job again. (nonrestrictive)
- The gentleman who is standing by the fireplace is a well-known composer. (restrictive)
5. Use a comma to set off appositives
Rule: An appositive is a noun or noun phrase that renames a nearby noun. Appositives offer nonessential information. Nonrestrictive appositives are set off with commas; restrictive appositives are not.
- Alexander Pope, the Restoration poet, is famous for his monologues. (appositive)
- The poet Pope is famous for his monologues. (no appositive)
- The New York Jets, the underdogs, surprised everyone by winning the Super Bowl. (appositive)
6. Use a comma to indicate direct address
Rule: When a speaker in a sentence names the person to whom he is speaking, this addressing of his audience is called direct address. Direct address is indicated by the use of a comma or commas, depending upon its placement within the sentence.
- I think, John, you’re wrong.
- John, I think you’re wrong.
- I think you’re wrong, John.
7. Use commas to set off direct quotations
Rule: A dialogue is a conversation between two or more people. If the speaker (not the listener) in the conversation is identified, his name, (or the noun or pronoun used to refer to the speaker), and the verb that refers to his speaking are enclosed within commas.
- Mary said, “I dislike concerts because the music is too loud.”
- “I dislike concerts because the music is too loud,” she said.
- “I dislike concerts,” proclaimed Mary, “because the music is too loud.”
8. Use commas with dates, addresses, titles, and numbers
Rules for dates: In dates, the year is set off from the rest of the sentence with a pair of commas. Example:
- On December 12, 1890, orders were sent out for the arrest of Sitting Bull.
Rules for addresses: The elements of an address or place name are separated by commas. A zip code, however, is not preceded by a comma. Examples:
- John Lennon was born in Liverpool, England, in 1940.
- Please send the letter to Greg Carvin at 708 Spring Street, Washington, IL 61571.
Rules for titles: If a title follows a name, separate the title from the rest of the sentence with a pair of commas. Example:
- Sandra Belinsky, MD, has been appointed to the board.
Rules for numbers: In numbers more than four digits long, use commas to separate the numbers into groups of three, starting from the right. In numbers four digits long, a comma is optional. Examples:
- 3,500 [or 3500]