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The Oxford comma, also known as the serial comma, is a punctuation mark that is used to separate items in a list. It is placed before the coordinating conjunction (usually "and" or "or") that precedes the final item in the list. For example, consider the following sentence without the Oxford comma: "I bought apples, bananas and oranges." Without the Oxford comma, it is unclear whether "bananas and oranges" are two separate items or if they are grouped together as "bananas and oranges." With the Oxford comma, the sentence would be: "I bought apples, bananas, and oranges." This clarifies that "bananas" and "oranges" are two separate items in the list. The use of the Oxford comma is a matter of style and there is debate among writers and grammarians on whether it should be used consistently or only when necessary for clarity. Some style guides, such as the Associated Press (AP) Stylebook, do not recommend the use of the Oxford comma except when it is necessary to avoid ambiguity. Others, such as The Chicago Manual of Style, recommend the use of the Oxford comma to avoid ambiguity in all cases. Ultimately, whether to use the Oxford comma or not is a stylistic choice, but it is important to be consistent within a given piece of writing.