<span>In English language punctuation, a serial comma or series comma (also called an Oxford comma or a Harvard comma) is a comma placed immediately before the coordinating conjunction (usually and or or) in a series of three or more terms.
</span> <span>The 'Oxford comma' is an optional comma before the word 'and' at the end of a list: We sell books, videos, and magazines. It's known as the Oxford comma because it was traditionally used by printers, readers, and editors at Oxford University Press.
</span> <span>These 3 sentences show why you should always use the Oxford comma. Follow Business Insider: An Oxford, or serial, comma is the last comma
in a list; it goes before the word "and." However, depending on the
list you are writing out, omitting it can lead to some confusion.
