punctuation - Should I use a comma before "and" or "or"?

Is using a comma then an "and" or an "or" after it proper punctuation?

Example:

• I fell over, and hurt my knee.


• Should I go, or not?

Answer

Whether it is correct to use a comma before a coordinating conjunction ("and", "but", "or", "nor", "for", "yet", "so") depends on the situation. There are three primary uses of conjunctions:

1. When a coordinating conjunction is used to connect two independent clauses, a comma is always used. Examples:

   
   
   
   
   
   • I hit my brother with a stick, and he cried.
   
   
   • The rain stopped, and the sun came out again.
   
   
   • Should I eat dinner, or should I play a game?
   
   



2. When a coordinating conjunction is used to connect a dependent clause, a comma is never used. This includes both of your given examples. Other examples:

   
   
   
   
   
   
   • The boy ran to his room and cried.
   
   
   • Frank is a healthy and active child.
   
   
   • Should I eat dinner or play a game?
   
   



3. When a coordinating conjunction is used to connect three or more items or clauses, a comma is optional (though I personally prefer to use one). Examples:

   
   
   
   
   
   • I bought cheese, crackers, and drinks at the store.
   
   
   
   • Should I eat dinner, play a game, or go to the store?