The Oxford comma is an optional comma that is also known as the serial or Harvard comma. It clarifies meaning when it is placed before conjunctions, such as or & and in a series of three or more terms in a sentence.
The Oxford comma got its name from the Oxford University Press where printers, editors and readers traditionally used it. It is somehow ironic that the PR department at Oxford University no longer uses the serial comma, but the Oxford University Press still does.
It is usually omitted in the UK, Canada and Australia, but it appears to be widely used in the United States, for instance by the American Psychological and American Medical Association. The majority of American style guides mandate the use of the serial comma, e.g. the Chicago Manual of Style (CMS) and the U.S. Government Printing Office Style Manual. However, The Associated Press, The Economist and the New York Times avoid it.
Occasionally, sentences with complicated lists require the Oxford comma, for instance:
“… highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector.” (This is in fact a real example from The Times of London.)
Nevertheless, there is a saying that “for every phrase that the Oxford comma clarifies, there is another for which it obfuscates”. For instance: “Through the window she saw John, a basketball player and some onlookers” clearly refers to two people and some onlookers. Throw in the Oxford comma and John becomes a basketball player: “Through the window she saw John, a basketball player, and some onlookers”.
This highlights that the Oxford comma is not a black-or-white, always-or-never thing. It is indeed a matter of style.
The American indie rock band Vampire Weekend released a song called “Oxford Comma” where they ask ‘who gives a f*ck about the Oxford comma?’. Apparently, quite a few people as the Oxford comma has a Facebook page with over 30,000 likes.
So why should you use the Oxford comma?
- It helps avoid ambiguity.
- It matches the natural speech pattern of pausing before the last item in a series.
- It makes lists easier to comprehend.
And why should you omit the Oxford comma?
- Sometimes it does not help clarity and can introduce ambiguity.
- It is redundant: the preceding conjunction serves the same purpose as the comma.
- It takes up more space.