The Oxford – or serial – comma is the one inserted just before the words “and” or “or” in the last item in a list of three or more items. That’s straightforward enough, but perform a simple search on the Internet on the search phrase “Oxford comma” and the results are sure to confuse you.
What is clear is that its presence, or lack thereof, is the subject of much debate. Many punctuation specialists argue that the use of an Oxford comma can make or break the meaning of a sentence, while others believe that it is an archaic outdated mark that should be confined to the past.
Read more: Comma rules everyone should master.
The truth is this: whether the Oxford comma is used is generally not so much of a big deal—you will see sentences on a daily basis both with and without it, and it really won’t cause you any serious issues. “I ran six miles, swam ten miles, and cycled twelve miles.” “I ran six miles, swam ten miles and cycled twelve miles.” Both sentences are perfectly fine and you won’t lose any credibility for the use of either of them. However, sometimes a missing Oxford comma can make a serious difference to the meaning of a sentence…
In this case, the Oxford comma is needed to resolve ambiguity and, as such, it is sometimes helpful to the reader to use an isolated serial comma for clarification, even if the convention has not been adopted elsewhere in the document. The key to mastering this, as with many things relating to punctuation, is to consider the context. In deciding whether or not to use an Oxford comma, always keep in mind your intended meaning. If those items in your series or list are equal but individual, you should ensure that they are all separated equally, and commas throughout and before the last item will help to keep your meaning clear.
Need help with your punctuation? Take a look at our punctuation cheat sheet.