What Is the Oxford Comma, and When Should You Use It?

The Oxford comma appears just before and or or in a sentence that lists three or more items.

We can buy two pies, one cake, or eight donuts.

The sentence above shows an Oxford comma example: it’s the comma after cake. This punctuation mark is also called the Harvard comma or the serial comma, which makes sense because it separates items in a series.

When to use the Oxford comma

Unlike most rules for comma use, using the Oxford comma is never truly a requirement. Whether you use it or not often depends on the English variant you’re writing in and/or the style guide you’re following.

For example, the Oxford comma is common in the US but practically despised in the UK, the home of Oxford University Press, which popularized it and for which it’s named (go figure). And it’s not used much in other English-speaking countries either.

When it comes to style guides, those outside the US tend to recommend using it only when a sentence would be unclear without it. Inside the US, these are some major style guides that call for the Oxford comma:

  • The Chicago Manual of Style
  • American Psychological Association (APA)
  • Modern Language Association (MLA)
  • The Elements of Style by William Strunk Jr. and E. B. White
  • Harvard University Press
  • The Bluebook

On the other hand, the US style guide most well known for avoiding the Oxford comma is Associated Press (AP) style, which is often used for journalistic publications and web content. In newspapers and magazines, the need to save space is paramount, so anything unnecessary must go. Therefore, an AP style Oxford comma is nearly nonexistent. Still, it’s allowed when clarity requires it.

Why use the Oxford comma

The point of the Oxford comma is clarity. So the time to use it is when you’ve written a list of at least three things and not separating them could lead to confusion. These are some examples:

  • I wrote letters to my friends, Madonna and Kamala Harris.”

It’s unclear whether the author is friends with Madonna and Kamala Harris or she wrote to these two people in addition to her friends.

  • His favorite breakfast consisted of ham and eggs, tomato slices and coffee and cream.”

Does this writer dunk his tomato slices in coffee and then drink some cream?

  • The software company’s aims are to create products that streamline processes by smoothing workflows, help its customers meet their evolving business goals and achieve new levels of innovation in the competitive software industry.”

Adding the serial comma would help make the three long items in this sentence more distinct.

Even when it’s not required for clarity, some people have recommended using it for other reasons. One is Herbert Spencer, the English scientist known for coining the phrase survival of the fittest. An entry for “,⁦ and” in a guide for authors and printers quoted his belief that adding the serial comma after each item in a list gave all the items equal weight and emphasis. This practice reflects the way we talk, pausing between listed items.

Why not to use the Oxford comma

The most fundamental argument against the serial comma is that it’s not necessary, and anything that’s not necessary is superfluous—it’s just clutter. Like other aspects of language, punctuation rules change with the times, and we’re currently moving toward minimalism.

Even without this shift in punctuation trends, the Oxford comma is most often simply not needed. However, it has both its true believers and its die-hard opponents. While some think it should be required, others point to the variety of other available ways to make a sentence clearer. We can use some of these methods to clarify the example sentences above without it:

  • I wrote letters to Madonna, Kamala Harris and my friends.

Changing the order in which you list the items often clears things up.

  • His favorite breakfast consisted of ham and eggs, tomato slices and coffee with cream.

Rephrasing works well too.

  • The software company aims to create products that streamline processes by smoothing workflows and helping its customers meet their evolving business goals. It strives to achieve new levels of innovation in the competitive software industry.

Another solution is to divide long sentences into shorter ones. Or you could format the sentence as a bulleted list.

Many style guides that require the serial comma do so because it’s the simplest way to guarantee separation between items in a list. But is it good writing? Opinions differ. Academic writing and technical writing are more utilitarian than, say, a literary novel, so they prioritize practicality and clarity over beauty. It’s all about what a writer is trying to accomplish.

Keeping the peace

Since there’s no universal English rule for using the Oxford comma, it’s a good idea to be Switzerland in this war—neutral and pacifist. The serial comma is ideal at some times, and not so much at others.

QuillBot offers a dependable way to keep all of those times straight. Its writing tools let you adjust the settings to account for typical usage in different countries, such as in Canada vs. the US. It also helps you cite sources properly in all the styles listed above, plus hundreds more.

Keep calm and write on with QuillBot.

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Hannah Skaggs

Hannah, a writer and editor since 2017, specializes in clear and concise academic and business writing. She has mentored countless scholars and companies in writing authoritative and engaging content.