A Definitive Guide to the Oxford Comma

An Oxford comma—also known as a serial comma—is a comma placed after the second-to-last item in a list of three or more. The use of the Oxford comma is a hotly debated topic among writers, editors, and proofreaders.

Are you puzzled about whether or not to include Oxford commas in your writing? In today’s post, we’ll clear up any confusion about this controversial punctuation mark, so you can be confident you’re using it correctly.

Oxford Comma Examples

The Oxford comma comes before the word “and” or “or” in a list of three or more items:

The recipe calls for flour, sugar, and butter.

I don’t have any biscuits, cake, or ice cream.

He was allergic to milk, eggs, nuts, and shellfish.

We’ve never been to France, Italy, Japan, or India.

When Should an Oxford Comma Be Used?

There are three situations in which the Oxford comma is required:

1. When your style guide advises it.
2. When you’re writing for a US audience.
3. When it makes your meaning clearer.

Let’s look at each of these in more detail:

1. Some Style Guides Dictate Use of the Oxford Comma

The most widely used style guides that encourage the use of the Oxford comma are MLA, APA, and The Chicago Manual of Style. It’s also required by Strunk & White’s Elements of Style, the US Government Printing Office Style Manual, and (unsurprisingly) the Oxford University Press and Harvard University Press style guides.

If you’re using one of these style guides, you should certainly use Oxford commas. If you’re following a different style guide, be sure to check its requirements. But watch out if you’re using the University of Oxford Style Guide—despite its name, it doesn’t advocate Oxford commas!

2. US English Usually Uses the Oxford Comma

Oxford commas are nearly always used in American English. The only exception is if your style guide says otherwise. So, always follow the advice of your style guide if you’re using one. But, if you don’t have a style guide and you’re writing with US readers in mind, you should use Oxford commas in your lists.

3. Use Oxford Commas to Avoid Confusion

Even if your style guide doesn’t require them and your audience isn’t American, there may still be times when you need to use an Oxford comma. Take a look at the following sentences:

I love my parents, Billie Eilish and Robert Downey Jr.

This dress is available in red, green, blue and white and yellow.

I bought broccoli, potatoes and a comic book for my son.

Each of these could confuse readers! The first could suggest that the writer’s parents are a 20-year-old pop star and the actor who plays Iron Man. It isn’t clear whether the dress in sentence two comes in blue and white, or white and yellow. And the third sentence implies that broccoli and potatoes were included with the comic book as a gift for the son.

All of these examples make more sense when you add an Oxford comma:

I love my parents, Billie Eilish, and Robert Downey Jr.

This dress is available in red, green, blue and white, and yellow.

I bought broccoli, potatoes, and a comic book for my son.

It’s now clear that the writer loves their parents, while they also love Billie Eilish and Robert Downey Jr. We understand that there isn’t a yellow-and-white version of the dress being described. And we are assured that the broccoli and potatoes weren’t part of the gift for the boy.

Summary: When to Use the Oxford Comma

The Oxford—or serial—comma is used after the penultimate item in a list of more than two things. If you’re following a style guide, it will tell you whether or not you should use Oxford commas in your work. However, if you’re not using a style guide, you should still use Oxford commas when you’re writing for US readers. Moreover, you should use them for readers on both sides of the Atlantic if your meaning would be unclear without them.

We hope our guide has settled the Oxford comma debate once and for all. However, if you’d like a punctuation expert to check your writing for misplaced or missing commas, our proofreaders can help. Why not send us a free sample today and see how we can help you refine your writing?