Title: READ: Commas in a List
Course: English 9 (B)

Commas in a List

The comma is a punctuation mark. It has the same shape as an apostrophe or single closing quotation mark in many typefaces, but it differs from them in being placed on the baseline of the text.

The comma is used in many contexts and languages, principally for separating things. According to the Oxford English Dictionary, the word comma comes directly from the Greek komma (κόμμα), which means something cut off or a short clause.

This exercise will look at the comma as it is used regarding lists. Commas are used to separate items in lists, as in They own a cat, a dog, two rabbits, and six mice. In English a comma may or may not be used before the final conjunction (and, or, nor) in a list of more than two elements. A comma used in such a position is called a serial comma or an Oxford or Harvard comma (after the Oxford University Press and Harvard University Press, both prominent advocates of this style). In some cases use or omission of such a comma may serve to avoid ambiguity:

Use of serial comma disambiguating:
- I spoke to the boys, Sam and Tom. – The boys refers to Sam and Tom (I spoke to two people).
- I spoke to the boys, Sam, and Tom. – The boys, Sam, and Tom are separate units (I spoke to four or more people).

Omission of serial comma disambiguating:
- I thank my mother, Ayn Rand and God. – The writer is thanking three people: the writer's mother, Ayn Rand (who is not the writer's mother) and God.
- I thank my mother, Ayn Rand, and God. – The writer is thanking two people: Ayn Rand (who is the writer's mother) and God.

If the individual items of a list are long, complex, affixed with description or themselves contain commas, semicolons may be preferred as separators, and sometimes the list may be introduced with a colon.

Source: http://en.wikipedia.org/wiki/Comma