Punctuation helps the reader understand a story. Commas, periods, dashes and other marks convey the writer's voice. They signal an emphasis or tone in language, as well as tell a reader when to stop or pause. Here are some guidelines for using commas.

If a word or phrase is essential, do not put commas around it.

  • Essential: People who eat a lot of cookies may gain weight.
  • Nonessential: My sister, who eats a lot of cookies, never gains weight.

Here's another way to think about what's essential.

  • My husband, Bubba, finished driving school. (I have one husband. His name is not essential to the sentence.)
  • My husband Bubba finished driving school. (I have lots of husbands, so the reader needs to know which one.)

Use a comma before a conjunction that joins two clauses that could stand alone.

  • The police found the gun lying 10 feet away, and they began dusting the area for fingerprints. (Use a comma. Each clause has a subject and verb.)
  • The police found the gun lying 10 feet away and began dusting the area for fingerprints. (No comma. The sentence has only one subject, used with compound verbs.)

Use a comma after most introductory clauses or phrases.

  • Just as the pilot stepped into the cockpit, the first alarm sounded.
  • Irritated, she turned around and climbed back out.

The comma goes before the conjunction, and only if the conjunction joins two independent clauses.

  • Wrong: Legislators thought they had finished for the session but, the governor called them back.
  • Right: Legislators thought they had finished for the session, but the governor called them back.

However, parenthetical material after a conjunction needs to be set off with commas. (Although if you need this many commas, you may want to revise the sentence.)

  • Right: Poll workers said they didn't see many voters, but, at county offices, election officials reported a high voter turnout.

Taken from Cleaning Your Copy, a self-directed course at Poynter NewsU.

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