Also known as the serial comma, the Oxford comma can be a tricky subject, as well as a disputed one. It is commonly known as the Oxford comma because its use is advocated by the Oxford University Press (and the Harvard University Press too). Essentially, it is a comma that is placed before the ‘and’ that comes before the last element in a list.
Here is an example of such a list where the Oxford comma is absent:
Talking in the group was John, Martin’s father and a trained helicopter pilot.
Without the Oxford comma, it’s hard to tell exactly what’s going on. Are there three people – John and Martin’s father and a trained helicopter pilot? Or two – John (Martin’s father) and a helicopter pilot? Or is just a very busy John, who is Martin’s father and a helicopter pilot?
Throw in the Oxford comma, and the sentence takes a step closer to clarification:
Talking in the group was John, Martin’s father, and a trained helicopter pilot.
Now we know that there is more than one person talking in the group. There is John and there is the helicopter pilot. I’m sure you’d agree this is slightly less ambiguous. But, in this case, it still doesn’t quite clear things up…
We can see in this example a drawback of the Oxford comma – it can sometimes reduce one ambiguity while enhancing another. Without the full context of this story, there is still ambiguity. With this sentence there could well be three people talking: first John, then Martin’s father, then the pilot. Or there could be just two: John (Martin’s father) and the pilot.
Make sure you identify these ambiguous situations and resolve them accordingly. Perhaps, in this case, simply by adding ‘who was’ or ‘who is’ before ‘Martin’s father’.
Talking in the group was John, who was Martin’s father, and a trained helicopter pilot.
If your story has already established whether John is Martin’s father or not, then no clarification will be needed.
This is more of the situation I find myself in when writing fantasy:
His sword was by his side, over his shoulder fluttered a dark cape and a long shield covered is arm.
Some readers will read: …over his shoulder fluttered a dark cape and a long shield… and will, in that quick and automatic reading process, read that the shield is also fluttering over his shoulder. The rest of the sentence should make it clear what is meant, but the reader may have to go back and read it again – suddenly they’ve been taken out the story. Not every reader will stumble at this sentence – maybe just one or two out of ten. But the oxford comma can save the day for everyone:
His sword was by his side, over his shoulder fluttered a dark cape, and a long shield covered his arm.
In my opinion, much better – but because there is no obvious ambiguity, it is far from compulsory. It all comes down to what works for you and what works for your readers.
The Oxford comma is also useful when one of the items in a list already contains the word ‘and’:
My favourite meals are fajitas, curry, fish and chips and lasagne.
Not terribly confusing, but a little awkward. An Oxford comma after chips and it reads more easily.
If you detect ambiguity in your writing, or maybe just notice it doesn’t read how you intended, then experiment with the Oxford comma and consider whether it works for you or not. Don’t worry about the arguing pundits for and against the Oxford comma, judge each case as it comes and remember that clarity is vital.
I hope this writing guide has helped you understand how to use an Oxford comma. We also have other writing guides on Punctuating Dialogue, Establishing Characters and Run on Sentences. If you want to hear when publish new writing guides, as well as our own fiction, writing articles and book reviews, then subscribe or follow us @Sentient_Ink.