Commas are used for a variety of functions. Here's a list of the most common uses.
1. Use a comma before a coordinating conjunction like "and," "but," or "or" that joins independent clauses.
For example:
Nearly everyone had arrived, but the guest of honor was late.
2. Use a comma after an introductory phrase or clause. These introductory phrases often establish setting, either time or location.
For example:
Near a small stream, the park rangers discovered the abandoned shack. In 1988, the shack had been abandoned.
3. Use commas between all items in a list or series.
For example:
Bubbles of air, leaves, ferns, and bits of wood are found trapped in sap.
4. Use a comma between two or more adjectives that each modify a noun separately, called coordinate adjectives.
For example:
Robert is a handsome, brave, and generous man.
5. Do not use commas between adjectives that modify a noun when placed together, called cumulative adjectives.
For example:
Three large grey shapes moved towards us. NOT Three, large, grey shapes moved towards us.
6. Use commas to set of phrases if they could be eliminated from the sentence without changing its meaning.
For example:
The helicopter, with its spotlight, circled above.
7. Use commas to set off transitional phrases.
For example:
As a matter of fact, American football dates back to the Middle Ages.
8. Use commas around parenthetical phrases.
For example:
Evolution, as far as we know, doesn't work this way.
Use commas to set off other elements of a sentence.
For example:
- Names when directly addressing a person: Forgive us, Mrs. Smith, for breaking the dish.
- The words "yes" and "no": Yes, I'll be there at 6:00.
- Tag questions: The book was better than the movie, wasn't it?
- Interjections: Well, it's difficult to say.
Use commas in numbers, addresses, dates, and titles.
For example:
- Numbers: 20,000
- Addresses: 123 Main St., Marquette, MI 49855
- Dates: On July 4th, 1776, the Declaration was signed.
- Titles: Susan Hawkins, M.D., will present her theory at the meeting.