Punctuation — Commas

About half of the errors in punctuation are comma errors. This writer’s guide is a quick reference for you, so you won’t make the most common errors with commas. The guide will not cover all of the minute details of commas, just the ones we use most often.

1. Commas set off independent clauses which are joined by a coordinating conjunction
   The chairman is Shauna Sloan, (comma) and the president is Jamie Harris.
2. Commas set off introductory elements.
   1. Adverb clauses:
      If you register now, (comma) you can vote by mail.
   2. Long prepositional phrases:
      In the cool air of the April morning, (comma) we prepared for the track and field meet.
   3. Verbal phrases.
      Speaking off the record, (comma) the Senator addressed the senior class.
3. Commas separate the items in a series when there are more than two items.
   The book is available in book-stores, (comma) at newsstands, (comma) or by mail.
4. Commas separate coordinate adjectives when they are of equal importance.
   Tall, (comma) stately trees lined the boulevard.
5. Commas set off parenthetical expressions. These words or phrases interrupt the flow of the sentence and are not essential to its meaning.
   1. General parenthetical expressions:
      She was, (comma) in my opinion, an outstanding leader.The entire speech, (comma) moreover, (comma) lacked vitality.
   2. Nonrestrictive (nonessential) clauses:
      Parsons Boulevard, (comma) which runs past my house, (comma) is being repaved.
   3. Nonrestrictive (nonessential) phrases:
      Mrs. Atlee, (comma) wearing red, (comma) is the ambassador’s sister.
   4. Nonrestrictive (nonessential) appositives:
      America’s first general, (comma) George Washington, (comma) started his own navy.
6. Commas set off absolute phrases.
   The day being warm, (comma) we headed for the beach.
7. Commas set off names or words used in direct address.
   Carole, (comma) what are you doing?
8. Commas set off yes or no at the beginning of a sentence.
   Yes, (comma) there is a lot of reading to this course.
9. Commas set off mild interjections.
   Well, (comma) I’ll have to think about that.
10. Commas set off explanatory words like she said from direct quotations.
    Churchill said, (comma)  “Short words are best.”
11. Commas set off examples introduced by such as, especially, and particularly.
    John enjoys outdoor sports, (comma) such as football and hunting.
12. Commas replace omitted or understood words.
    Captain Franklin attended West Point; his brother, (comma)  the Coast Guard Academy
13. Commas separate confirmatory questions from statements.
    It’s cold in here today, (comma) isn’t it?
14. Commas set off the greeting and complimentary close of letters.
    Dear Mabel, (comma) …Sincerely, (comma)
15. Commas set off the elements of dates and addresses.
    On March 3, (comma) 1984, (comma) we had a blizzard in Kansas. He lives at 321 Maple Street, (comma) Kokomo, (comma) Indiana.
16. Commas group words to prevent misreading.
    After eating, (comma) the boys became sleepy (Not “after eating the boys…”).Inside, (comma) the dog was growling (Not “Inside the dog…”)