When you write a list of three or more items, unless you display them as a bulleted or numbered list, you conventionally separate the items with either a comma or the word ‘and’ (or sometimes ‘or’). You may choose to separate the last two items in the list with just the word ‘and’, or with a comma followed by ‘and’:

• Her shirt was red, green and blue.
• Her shirt was red, green, and blue.

If you choose the second option, you’re using the Oxford comma, also called the serial comma. This little punctuation mark arouses surprisingly strong emotions: many people will be happy to tell you that omitting the Oxford comma is simply wrong. Others will assert it is both unnecessary and ugly.

A brief search will reveal many, many articles both in favour of and against its use.

Reducing ambiguity

One argument in favour of this comma points to ‘ambiguous’ sentences like the following, taken from Steven Pinker’s book, The Sense of Style :

• Among those interviewed were Merle Haggard’s two ex-wives, Kris Kristofferson and Robert Duvall.
• This book is dedicated to my parents, Ayn Rand and God.
• Highlights of Peter Ustinov’s global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector.

Another example – ‘We invited the strippers, JFK and Stalin’  – triggered headlines around the world when a Texas schoolteacher turned it into a cartoon  to illustrate the distinction between its meanings with and without the final comma.

I have a number of problems with all these examples:

• They are carefully constructed to appear ambiguous, while at the same time having only one reasonable interpretation.
• While they are funny and clever, they don’t really demonstrate ‘why the Oxford comma is important ’. Each sentence could be clarified in many other ways.
• If some of the people in a list are named, they should all be named; to do otherwise is discourteous.

Thanks to the writer’s parents are frequently used as examples. But if I wanted to thank and name my parents, I could simply write:

I’d like to thank my parents: Max and Betty.

or

I’d like to thank Max and Betty, my parents.

If I wanted to thank my parents and two other people, I could write:

I’d like to thank John, Mary and my parents.

or

I’d like to thank John, Mary, and my parents, Max and Betty.

What’s more, in some cases the Oxford comma doesn’t remove ambiguity: Joe Kessler  points out that if the Texas schoolteacher’s strippers are replaced by a single stripper, the sentence with the Oxford comma – ‘We invited the stripper, JFK, and Stalin’  – is the ambiguous one.

In February 2014, truck drivers in Maine sued for overtime pay. The argument centred on the question of whether ‘packing for shipping or distribution’ was one activity or two; the court held that it was only one, and the drivers were entitled to paid overtime .  If you’re writing legislation, it’s a good idea to make sure that the only reasonable interpretation is the one you intended: don’t make people go to court over a comma!

Complex lists

There is a case for using the Oxford comma where each item in the list is more than a single word.

John had an essay due that night, so he cleaned the bathroom, weeded the vegetable patch, and watched the first three episodes of Buffy the Vampire Slayer.

The shirts are available in green and brown, pink and purple, and blue and white.

In most non-fiction, on or off the web, I would display this sort of information in a bulleted list, thereby dodging the issue altogether.

The shirts are available in:

• green and brown
• pink and purple
• blue and white.

Make a decision

I prefer to avoid the Oxford comma. The trend in recent years has been towards reduced punctuation, so why use this comma anywhere it’s not really necessary?

In the end, your decision to use the Oxford comma, omit it, or use it only where required for clarity (as recommended by the Australian Style Manual ) is a question of style, not substance.

So make your decision and record it on your editorial style sheet.

Then relax!