The Oxford comma: What it is and when to use it

The Oxford Comma looks no different to a normal comma but its usage is one that causes controversy among editors and writers. Also known as the series comma, serial comma and Harvard comma, it is the comma that would go in a list of items before the “and” or “or” that precedes the last item in the list. So, for example, the first of the following sentences uses the Oxford Comma whereas the second does not:

• The items he put into the van included screwdrivers, white paint, a hammer, and a flask of hot coffee.
• The items he put into the van included screwdrivers, white paint, a hammer and a flask of hot coffee.

In a fairly straightforward list such as the above the decision comes down to style and preference. There are also national differences. Most schools in England, for example, teach that the Oxford Comma should never be used for simple lists whereas in the USA the norm is for it always to be used in lists containing three or more items.

Fowler on the Oxford comma

In Fowler’s Modern English Usage, it points out that the use of a comma in lists is to replace the word “and”, otherwise the list above would read:

• The items he put into the van included screwdrivers and white paint and a hammer and a flask of hot coffee.

Fowler argues that there is no need therefore for the final comma in a list as the word “and” is still there. He does, however, acknowledge that there are cases where, to avoid ambiguity, it should be used if the items in the list are more complex.

House styles on the Oxford comma

The house styles of magazine and newspapers in England try to deal with this by specifying when and where it should and should not be used. The norm is not to use it except in certain circumstances. A common example is to have no comma before the "and" unless the list itself contains the word "and".

The following two sentences show that in practice:

• The items he put into the van included screwdrivers, white paint, a hammer and a flask of hot coffee.
• The items he put into the van included screwdrivers, red and white paint, a hammer, and a flask of hot coffee.

An extra rule that some magazines in England adopt is if the list itself includes a comma, then start the list with a colon and use semi-colons to separate the items, including before the "and". So, in the above example:

• The items he put into the van included: screwdrivers; red, black and white paint; a hammer; and a flask of hot coffee.

In conclusion, there is no right or wrong in the use of the Oxford Comma for simple lists and it is a matter of writer’s preference or house style. However, if there is a danger of ambiguity that the Oxford Comma would solve, then it should be used. Likewise, if using the Oxford Comma would create ambiguity that was not previously present, then it should not be used.