Online Learning Resources
1. Use a comma to separate independent clauses (complete sentences) when they are joined by the coordinating conjunctions and, but, or, nor, for, so, yet.
The students studied all night for the test, but no one made a passing grade.
Every computer in the lab was in use, so I walked all the way to the library in the cold.
Note: Beware of comma splices, an error which occurs when two complete sentences are joined with only a comma and no coordinating conjunction.
The lab assistant checked her results, she didn't want to make a mistake. --incorrect
The lever should be switched to full power, sealant should then be applied. --incorrect
2. Use a comma after long introductory clauses, phrases, or words that come before the main clause.
If every student in our club helped, this fundraiser would be our most successful yet.
Because he forgot to set his alarm, he was late for class.
At the racetrack, Henry won enough money to buy everyone dinner.
3. Use a pair of commas in the middle of a sentence to set off phrases, clauses, and words that are not essential to the meaning of a sentence.
My teacher, Katherine Grey, told me I should study more.
Apples that are green are usually Granny Smith apples. (essential clause)
Drivers who have been convicted of drunken driving should lose their licenses. (essential clause)
Apples, which are my favorite fruit, are a convenient sack lunch item. (non-essential clause)
The students protesting the assignments refused to come to class. (essential clause)
The students, protesting the assignments, refused to come to class. (non-essential clause)
4. Use a comma to separate three or more words written in a series.
I earned an A in calculus, physics, English, and history last semester.
I sent the memo to Accounting, Marketing, and Research and Development.
Diners have a choice of broccoli, green beans, peas, or carrots.
5. Use a comma to separate two or more coordinate adjectives that describe the same noun.
Coordinate adjectives usually:
Can be written in reverse order
Make sense with an AND between them
She was a greedy, stubborn child. (coordinate adjectives)
The cracked bathroom mirror reflected his face. (no coordinate adjectives)
6. Use a comma to set off geographical names, items in dates (except month and day), addresses, and titles in names.
Birmingham, Alabama, gets its name from Birmingham, England.
This letter concerns the memo I sent on July 23, 2001, to every member of the staff.
Thousands swarmed the wall in November, 1989, to demolish it.
N. Katherine Hales, Ph.D., will be the lecturer today.
7. Use commas to set off direct quotations and dialogue.
The manager replied, ?I think we all want to complete this project.?
8. Use commas anywhere in the sentence to prevent possible confusion or misreading.
To Jonathan, Eliot had been a sort of mentor.
When he cooks, John often makes a mess.
Created by April Whitman, University of Oklahoma