Commas

1. Strong separation
   1. Use a comma to separate independent clauses that are joined with a conjunction (and, but, or, nor, for, yet, so).
      • Jack fell down the hill, and Jill came tumbling after.
      • The movie was over, but nobody left the theater.
      • It's time to study, so it's time to make coffee.
   
   
2. Internal separation
   1. In a series of three or more parallel elements, use a comma after each term. This includes short independent clauses used in a series (see third example).
      • The flag is red, white, and blue.
      • Joey walked into the room, shook his head, and sat down.
      • I came, I saw, but she conquered.
      
      
   2. Use a comma to separate a series of adjectives that describe the same noun.
      • The tall, stately trees lined the highway.
      • He's wearing an expensive, well-tailored suit.
      
      
   3. Use a comma to separate items in addresses, dates, and titles.
      • Birmingham, Alabama, gets its name from Birmingham, England.
      • July 4, 1776, is an important date.
      • Frank Nelson, M.D., will speak at the banquet.
      
      
   4. Use a comma to contrast elements in a sentence.
      • I met George, not John.
      • She is a lawyer, not a doctor.
      
      
   5. Use a comma to separate an independent clause from a question dependent on the clause.
      • You will pay the bill, won't you?
   
   
3. Introduction
   1. Use a comma after an introductory yes or no.
      • Yes, I was there.
      
      
   2. After an introductory phrase, use a comma.
      • On turning the corner, George ran into Miss Ware.
      • To get a ticket, we had to threaten the people in front of us.
      
      
   3. Use a comma after an introductory clause.
      • After the class is finished, we can get coffee and doughnuts.
      • Since I last saw you, I have won the lottery.
   
   
4. Enclosure
   1. Use commas to enclose words, phrases, and clauses that are not essential to the sentence.
      • She was, however, too tired to make the trip.
      • The nursery school, on the other hand, is self-sustaining.
      • David Smith, who is a junior, won first place.
      
      
   2. Use commas to enclose words in a direct address.
      • You, my friends, will be rewarded.
      • It is up to you, Christopher, to collect the rent.
      
      
   3. Use commas to enclose expressions such as he said or she replied.
      • "It is odd," Billy said, "to see the farm again."
      • "I know," she replied, "that we'll be glad we came."
   
   
5. Clarity
   1. To prevent misreading, use a comma.
      • Above, the mountains rose like purple shadows.
      • Soon after, the minister entered the chapel.
      • As far as I can see, the results have not been promising.
   
   
6. A final thought on comma usage
   • When in doubt, leave it out.