also known as the serial or the Harvard comma

What is the Oxford Comma?

The Oxford comma is a name given to the mark of punctuation used before the final and when listing a series of items. Here’s an example.

There were a number of items on the table: a handbag, a penknife, a clock, and a walking stick.

The Oxford comma is the comma which comes before the last item – , and a walking stick.

The Oxford comma gets its name from the fact that is has traditionally been recommended by the Oxford University Press in its instructions to typesetters and printers. The latest OUP style guide, New Hart’s Rules continues to urge its use. It’s also known as the ‘serial comma’, or the ‘Harvard comma’ in the USA.

When a number of items are listed in a sentence, the normal way to present them is separated by commas. However, there are two schools of thought about the need for the final comma.

The sentence above would still be understandable if it were written as follows:

There were a number of items on the table: a handbag, a penknife, a clock and a walking stick.

Some people argue that the final comma can be omitted in many cases because it breaks up the natural flow of the sentence. That’s true in this example – but only because all the items are quite distinct and carry equal weight. The comma in this case can be used or omitted. However, in other cases ambiguity can easily arise if the comma is omitted.

This is particularly true if the list includes things of a different kind.

cider, real ales, meat and vegetable pies and sandwiches

This example could mean that in addition to cider and real ales, the list includes meat, plus vegetable pies, plus sandwiches. But is more likely to mean meat and vegetable pies, plus sandwiches.

A famous instance of the same thing is that attributed to the American science fiction writer Teresa Hayden, who dedicated one of her books in the following way.

To my parents, Ayn Rand and God.

What she meant of course was ‘I am dedicating this book to my parents, to Ayn Rand, and to God’. Even that would have been pretentious enough, but the way she has expressed it, without the Oxford comma, the implication is that her parents were Ayn Rand and God.

A comma after the final and is not required when the last two items are a single expression or a ‘pair’

The menu offered us several options: roast beef, pasta bake, lamb chops, or fish and chips.

The comma should also be used if there is a grammatical extension to the list, as in this example.

brass, copper, bronze, and other non-ferrous materials

The need for the final comma become more acute when the list is a series of clauses in a single sentence.

The main points to consider are whether the competitors are skilful enough to complete the course, whether they have trained sufficiently for such a long race, and whether they are used to running at high altitude in these temperatures.

The commas in this example help the reader to understand a long statement made up of complex parts.

When the clauses in a complex sentence are themselves puctuated by commas, the separate clauses should be punctuated using the semicolon.

The outbreak of war was caused by a number of factors: Hitler’s determination to occupy Austria, Czechoslovakia, and Poland; the longstanding desire of Chamberlain and Daladier, as opposed to Winston Churchill, to avoid war at all costs; and Stalin’s cynical, last-minute pact with Hitler.

Even though the comma before the final ‘and’ is sometimes not required, it’s worth noting that it is never wrong. This is a good argument for always using it – to remove any possible ambiguity.

© Roy Johnson 2011

More on dictionaries
More on language
More on literary studies
More on writing skills
More on creative writing
More on grammar