What Is the Oxford Comma and Why Is It Important?

•  Jan 2019

•  5-minute read

•  Writing Tips

The Oxford comma, also known as the serial comma or Harvard comma, is the name given to the final comma in a list of three or more items. The Oxford comma gets its name from the house style of Oxford University Press, a historic publishing company based in the UK.

As an example, consider the following two lists:

You’ll see that both examples are punctuated differently, right? Specifically, the Oxford comma comes right after “Germany” in the second example, while Example 1 doesn’t use the Oxford comma at all.

So, should you use the Oxford comma in your own writing or shouldn’t you?

Simply put, opinions differ on the use of the Oxford comma. Speaking very generally, writers using British (UK) English tend to avoid the Oxford comma, while in American (US) English, the Oxford comma is relatively common. However, as with everything, exceptions exist in both cases.

One notable exception is The Oxford Style Manual, which suggests that the Oxford comma should be used wherever its absence would lead to confusion or ambiguity.

For example:

In Example 3, the absence of the Oxford comma obscures the fact that “William and Mary” is the second list item. However, with the Oxford comma in Example 4, this problem is solved, since a comma is placed immediately before the coordinating conjunction (in this case, “and”).     

When push comes to shove, then, your use or avoidance of the Oxford comma is generally up to you. However, whatever decision you make, try to be as consistent as you can, and always remember to use English language punctuation in a deliberate way.

If you’re writing a scientific paper or a technical document, you might also want to think about how your omission or use of the Oxford comma could generate unwanted ambiguity. At the same time, if you’re writing a document where unambiguous language isn’t a necessity, you might opt out of the Oxford comma for aesthetic reasons.

Perhaps most importantly, take note of the American style guides mandating the use of the Oxford comma, which include The Chicago Manual of Style, The MLA Style Manual, and APA Style. Also, don’t forget that The Oxford Style Manual requires the Oxford comma in some cases.

On a final – slightly amusing – note, try not to overlook the strange misunderstandings your omission of the Oxford comma may produce!

Without the Oxford comma, a reader might interpret Example 5 as stating that you had lunch with your father, and that your father is both Barrack Obama and the Prime Minister of Switzerland. To minimise the confusion, we can use the Oxford comma:

This solves the problem, right? Well – kind of …

In fact, Example 6 now showcases one of the surprising qualities of the English language! In using the Oxford comma, we solved one problem, but we created another: in particular, it’s now unclear whether “Barrack Obama” is an appositive describing the “father”, or whether “Barrack Obama” is the second item in a three-item list.

For some, the appositive problem makes the Oxford comma completely useless. However, for others, they see the Oxford comma as the lesser of two evils, and – as a result – they use it habitually. In truth, both are totally reasonable viewpoints.

So, having discussed the Oxford comma, you might now find it useful to learn more about appositive phrases.