When is it appropriate to use the Oxford, Harvard, or series comma?

Question

The Oxford comma, which is the term recognized more often than Harvard or series comma, has a string of matching attributes. For example; "We had an extraordinary pizza last night for dinner; we enjoyed tomatoes, ham, mushrooms, green peppers, and pineapple."

In the sentence above, all of the ingredients were listed that appeared on the pizza. While the majority of the ingredients were simply added by placing commas between the listed items, notice the words "peppers" and "and pineapple," you'll notice a comma. When listing three or more objects, the comma belongs right before the coordinating conjunction (and, but, or).

While the United States considers the Oxford comma important, other countries such as Britain, would create the sentence in the identical manner, but not include the coordinating conjunction. The sentence would then read, "We had an extraordinary pizza last night for dinner; we enjoyed tomatoes, ham, mushrooms, green peppers and pineapple." Notice there is no comma before the conjunction "and" in this sentence. So, while it's unacceptable to use the comma in some countries, some countries prefer its use.

Answer 1

This is a comma placed immediately after the penultimate term (i.e., before the coordinating conjunction, such as and or or) in a series of three or more terms.