Never put a comma before 'and': truism or myth?

Many teachers and parents have favourite grammatical rules that are trotted out at every opportunity. One of the commonest is ‘never put a comma before and’. Generally applied to lists, the sentence ‘He chose apples, bananas, and grapes’ brings out the schoolmasterly red pencil and is corrected to read ‘He chose apples, bananas and grapes’. The amendment is usually harmless, but applied blindly the results can be chaotic.

Grammar serves one single purpose: to ensure accurate communication. The danger of ungrammatical writing or speaking is simply that the meaning can be misunderstood. The purpose of punctuation for a writer, therefore, is to guide the reader through the words so that ideas are conveyed both accurately and easily.

Although this supposed rule about commas is often quoted some people take the opposite view and the question causes much debate. The use of a comma before and is, in fact, optional. In the example used above the removal of the comma after bananas makes no difference to the meaning, so either sentence will pass the test and convey accurate information. The optional comma before the last element in a list has impeccable credentials; it was invariably used by Oxford University Press and so for many years was termed an Oxford comma.

There can be practical problems for writers who implement the mistaken ‘no comma before and’ rule, in that the use of commas in complex lists is sometimes essential to guide and inform the reader. Consider the following statements:

She chose different flavours of crisps: plain, bacon and cheese and onion.

She chose different flavours of crisps: plain, bacon, and cheese and onion.

The first example is not clear and the reader stumbles over the meaning. Did she pick bacon and cheese crisps? Cheese and onion crisps? Or were there four flavours: plain, bacon, cheese, and onion?

In this case, the precise meaning is probably unimportant (unless it is a key fact in a fictional murder plot). In academic writing, however, it is essential that lists conveying methodological alternatives, information about sites of case studies, or references to multiple publications, for example, can be readily split into their component parts and accurately understood. In cases such as these the Oxford comma should be a requirement, not an option.