1. USE A COMMA TO JOIN TWO COMPLETE SENTENCES (MAIN or INDEPENDENT CLAUSES) WITH A CONJUNCTION (and, but, or, nor, so, yet, for).

   Subject + Verb + (Object) , CONJUNCTION + S + V + O . 

   	The RESET command affects field access, and the SEARCH command affects the filing.
   	Both methods are acceptable, but we have found the second method most effective.

   We thought the methodology was correct, so we tried the experiment again.

   However: S + V + O CONJUNCTION + V + O . (NO COMMA)

   The RESET command affects the field access and controls the filing arrangement.

2. USE A COMMA AFTER AN INTRODUCTORY PHRASE (INCLUDING SUBORDINATE CLAUSES THAT INTRODUCE A SENTENCE).
   
   INTRODUCTORY PHRASE , S + V + O.

   For many years, researchers have been looking for the answer. In Britain during the same decade, people began to worry about inflation.

   SUBORDINATOR  S + V + O , S + V + O. [link to transition word page]

   	Although he was president, he still felt insecure.
   	While most accountants wear suits, few engineers do.
   	Because the problem was so complicated, few researchers were willing to deal with it.
   	When we finish this step, we will write a proposal for the next project.

   However: S + V + O SUBORDINATOR S + V + O. (Usually, we use no comma when the subordinate clause comes at the end of the sentence.)

   We will write a proposal for the next project when we finish this step.

3. USE A COMMA TO INDICATE A PHRASE IS PARENTHETICAL (not necessary to the meaning of the sentence).
   
   Note: often when a phrase or clause can be moved in the sentence, it should be separated from the sentence with commas.

   	You should have asked Mary, who left yesterday. (We know Mary.) You should have asked the woman who left yesterday. (We don't know which "woman.") Johnson, the temporary chairman, called the meeting to order.
   	Haiti, a country that has been ruled various dictators for many years, is one of the poorest countries in the hemisphere.
   	I wish, by the way, you had talked to me sooner.
   	However, you should talk to me whenever you need to.

4. USE COMMAS WITH LISTS. Use a comma when each element has the same importance or when the order of ideas can be interchanged.
   

   	The finished product is a comfortable, sleek, modern cruiser.
   	We need a new computer, a new printer, and better software.
   	The light, brown bag broke. The brown, light bag broke. The light brown bag broke. ("light brown" refers to color)
   	The court, the governor, and the house and senate concurred.

5. USE COMMAS IN OTHER CONVENTIONAL WAYS:

Phil Druker © 2006  

thompson@uidaho.edu