Commas

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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.

     Example:

     Sunlight glittered on the lake, and birds chirped in the trees.

     BUT

     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.

     Example:

     A meticulous, thorough editor is essential to producing professional content.

     BUT

     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.

     Examples:

     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.

     Examples:

     She said, “Don’t touch that stove!”

     BUT

     “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).

     Example:

     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.

     BUT

     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).

     Examples:

     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.)

     BUT

     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.

     Example:

     What the problem is, is not clear.

  • Use a comma to set off a direct address.

     Example:

     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.

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