What’s an Oxford comma? How do I use it correctly? And do I need one at all?

I’ve got a book on my shelf printed by the Oxford University Press and another printed by the Cambridge University Press. The Oxford University book uses the Oxford comma. Not surprising. However, in the Cambridge University book, I noticed something that made me chuckle. There was a complete absence of Oxford commas. 

Coincidence? 

I wonder…

An Oxford comma is sometimes called a serial comma, and it is the comma preceding the and or the or before the final element in a series.

That could be a series of words or a series of phrases. Watch out for the Oxford commas in these examples. They’re red.

Blue, orange, and yellow

Cars, buses, motorcycles, or bicycles

Apples and mangos, bread and jam, or tea and biscuits

Good, solid, clean, and fresh

He sped past the newsagent, rounded the corner, and ducked behind a wall.

Jumping on the trampoline, running round the garden, and chasing bubbles, the children exhausted themselves.

When I walk to the shops, I must be careful to walk as a responsible pedestrian, careful that I do not forget to purchase every item on the shopping list, and careful that I carry any fragile purchases without banging them.

Here’s the tricky thing, though.

Cambridge University Press did not use Oxford commas, and Cambridge University is the last place I’d expect to find punctuation errors. There is, in fact, no right or wrong in the world of Oxford commas. 

Blue, orange, and yellow 

is as correct as 

Blue, orange and yellow

The challenge in this area of punctuation is maintaining consistency. Sometimes, I’ve seen manuscripts where one series of words or phrases has the Oxford comma, and the next doesn’t. Then, a page later, the Oxford comma returns. 

We start with the Oxford comma:

Cars, buses, motorcycles, or bicycles

Then it disappears:

He sped past the newsagent, rounded the corner and ducked behind a wall.

Then it’s back again:

Good, solid, clean, and fresh

This is an unfortunately easy situation to fall into. But I assure you, consistency is key.

Choose one way and stick to it. Inconsistency is an error that readers don’t see because they don’t search back through previous pages to check how something was done before. However, inconsistency can still trigger something in their memory, leaving them confused. Consistent manuscripts read more smoothly, and although the Oxford University and Cambridge University books had different comma policies, of course, they stuck to them perfectly from start to end.

Hopefully, now that you’ve got a clear definition of the Oxford comma—the comma preceding the and or the or before the final element in a series—inconsistency in this area will never trouble you again.

Finally, while I said that there is no right or wrong in the world of Oxford commas, I do think there is a case to be made for having them.

I’ll make it in the form of a story.

A customer emailed a t-shirt manufacturer, asking what colour t-shirts were available. The t-shirt manufacturer sent their reply, and they did not use an Oxford comma. The reply read like this: “We sell blue, black and white, yellow, orange, green and grey and pink t-shirts.” The customer understood the colours of the first four t-shirts, but they were terribly confused after that. Was there a green and grey t-shirt? Was there a grey and pink t-shirt? Was there a green one, and a grey one, and a pink one? Or was there a single t-shirt containing all three colours? The customer shook their head and contacted a different t-shirt manufacturer. This manufacturer used the Oxford comma, and the reply read like this: “We sell blue, black and white, yellow, orange, green and grey, and pink t-shirts.” Thanks to the Oxford comma, the customer could confidently place their order for a green and grey t-shirt.

Obviously, the book from Cambridge University Press, which didn’t use the Oxford comma, was still clear and accurate throughout. It did not have to overcome a situation as tricky as the one we’ve just discussed. Nevertheless, I choose to use the Oxford comma all the time. That way, no matter what I need to write, I will always be able to write it clearly.

Finally though, while I do recommend the Oxford comma wholeheartedly, my number one desire is to persuade you that consistency is key. The Oxford comma may not be the right policy for you, but consistency is the right policy for everyone.

I hope I’ve been of service. I will be back again next Friday, and I hope I’ll see you then.

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