The Serial Comma.

More here.... http://grammar.about.com/od/grammarfaq/ ... dcomma.htm



Question: What Is the Oxford (or Serial) Comma?
Answer:
The Oxford comma is the comma that precedes the conjunction before the final item in a list of three or more items:

This song is dedicated to Moe, Larry, and Curly.

This website is dedicated to Moe, Larry, Curly, Shemp, Joe, and Curly Joe.

This book is dedicated to my roommates, Nicole Kidman, and God.
The Oxford comma is so called because it has traditionally been used by editors and printers at Oxford University Press. New Englanders may favor the term Harvard comma (the convention is also followed by Harvard University Press). Throughout the U.S. the mark is commonly called the serial comma.

I think the top example is for zombies and cannibals.

I learned to use the Serial Comma when using a series of words in a sentence...though I know a lot of people who do not put the comma before the conjunction.

I was taught to use a comma before the conjunction so I would get in the habit of using it in the sentence.

I was taught not to use it.

I think it is required by some organizations for consistency within their publications. Personally, I use it when I think it aids in readability/understanding, leave it out otherwise.

I was marked off on papers if the serial comma was not used.

This book is dedicated to my roommates, Nicole Kidman, and God.

This is a bad example, perhaps. It gives the impression that there are three objects of dedication:
1. my roommates;
2. Nicole Kidman;
3. God.

It could be interpreted as: This book is dedicated to my roommates, (1) Nicole Kidman, and (2) God.

Arlen wrote:
It could be interpreted as: This book is dedicated to my roommates, (1) Nicole Kidman, and (2) God.

Then it would be "dedicated to my roommates, Nicole Kidman and God."

God, I'm glad you all aren't my roommates!