Commas are the most used (and abused) punctuation mark. Instead of falling into the trap of thinking you should insert a comma at each natural pause in a sentence, use this as a quick reference guide.
- Use a comma before a coordinating conjunction (and, but, for, or, nor, yet, so) that joins two independent clauses in a compound sentence. (An exception can be made if the clauses are very short.) Just be sure the conjunction is joining two clauses. Do not place a comma between the elements of a compound verb.
Sunlight glittered on the lake, and birds chirped in the trees.
Sunlight glittered on the lake and forced me to wear sunglasses.
- Use a comma between coordinate adjectives (two or more adjectives each separately modifying the same noun). You can tell adjectives are coordinate if they can be joined by “and” and placed in a different order. Do not place a comma between cumulative adjectives (adjectives that have to be placed in a certain order to make sense) or adjectives when one of them functions with the noun as a single unit.
A meticulous, thorough editor is essential to producing professional content.
She wore the long red dress.
A professional line editor is careful to preserve the author’s voice.
- Use a comma to separate three or more words or phrases in a series. If you are using The Chicago Manual of Style, place a comma before the last item in the series. If you are following The AP Stylebook, skip it, unless the meaning would be ambiguous without it.
Tom, Bill, and Suzy greeted me warmly. (Chicago style)
Tom, Bill and Suzy greeted me warmly. (AP style)
- Use a comma to separate quotations from dialogue tags. However, if the quotation needs a question mark or exclamation point, do not use a comma. Also, skip the comma if the quotation is a partial quote that flows with the sentence.
She said, “Don’t touch that stove!”
“Don’t touch that stove!” she said.
She said that the stove “was hot.”
- Use a comma to set off geographical locations and dates (when the month, day, and year are used).
She was born January 15, 1972, in New Berlin, Wisconsin, on a cold, snowy day.
- Use a comma to set off a word or phrase that introduces a sentence, particularly an interjection, an introductory participial phrase, a transitional word, or a dependent clause that precedes the main clause.
Examples (in the order they are listed):
Oh, I hope I am not late.
Running as fast as she could, she burst into the room.
Indeed, she was late.
Because my alarm clock did not go off, I was late to class.
I was late to class because my alarm clock did not go off.
- Use a comma to set off a word or phrase that is nonrestrictive; that is, it can be left out of the sentence without changing the meaning, particularly a parenthetical element or an appositive (that renames a noun).
The dog, who hates cats, spent his day barking up a tree. (Extra information)
She spoke to her mom, Clarice, on the phone. (She only has one mom. The name is a nonrestrictive appositive.)
The dog who lives in that yard spent his day barking up a tree. (Restrictive)
She spoke to her sister Julie on the phone. (She has more than one sister, so the name is restrictive and essential to clarifying which sister she called.)
- Use a comma to separate two words that might be unclear if they were read together.
What the problem is, is not clear.
- Use a comma to set off a direct address.
I will be home late, Dad.
Many questions about commas can be cleared up by deciding whether the word or phrase is restrictive or nonrestrictive. When in doubt, consult a style guide (or your friendly neighborhood copy editor). The Chicago Manual of Style and The AP Stylebook have helpful sections on punctuation and address a few rarer issues I did not discuss here. As always, the goal is ease of reading, so keep the reader in mind.