Want to start an argument in a group of editors? Bring up the serial comma. The serial (also called Oxford) comma is the comma that comes right before the conjunction in a list of items. For some reason, word people tend to get really worked up about this one little mark. (There’s even a song called “Oxford Comma,” but it should be noted that the song’s refrain wonders who really cares about it.)

The serial comma is not strictly necessary in many sentences, but other sentences do need it to clear up potential ambiguity. The Associated Press Stylebook, among others, says to omit it in simple series (note that this is not an outright ban), while other guides, including Strunk and White and the Chicago Manual of Style, say to always include it.

It’s unnecessary clutter, some say. It’s elegant and never unclear, others say. Both sides can trot out specially constructed (and sometimes quite funny) examples to bolster their cases:

• I’d like to thank my parents, Ayn Rand and God. (The classic example of a sentence that needs a serial comma)
• She told her best friend, Beulah, and her mother about her diagnosis. (Example of a sentence where a serial comma introduces confusion: Is Beulah the best friend, or is she another person?)

Because this is a style matter rather than a linguistic or grammatical one, reasonable people can disagree. The purpose of style guides is to ensure consistency, but not at the price of clarity.

Bottom line: follow your publication’s / workplace’s / client’s style on the serial comma and be done with it, bearing in mind that clarity trumps style every time. And save your energy — there’s plenty to argue about in English.