The Oxford Comma

The Oxford Comma, a comma which is written before 'and' or 'or' in a list, is used widely in punctuation but its necessity is still disputed.

Many use the Oxford Comma in all lists, regardless of meaning.

Example: Bring me a pencil, a ruler, and a pencil case.

In this example, the Oxford Comma is definitely redundant, but there are other examples where its usage becomes much more remunerative.

The Oxford Comma can be used to emphasise individual items as separate and distinct from other items in a list.

Here's a sentence:

Today, I bought some ice cream and topped it with chocolate, bubblegum and banana and strawberry sauces.

In the example above, the absence of extra punctuation makes it difficult to tell how the final items (underlined) relate to one another. Is one sauce bubblegum and banana; and the final, strawberry? Or is one bubblegum and the other banana and strawberry?

To clarify that the first sauce is bubblegum and banana, we can punctuate the sentence like so:

Today, I bought some ice cream and topped it with chocolate, bubblegum and banana, and strawberry sauces.

And to clarify, instead, that the final sauce is banana and strawberry, we can punctuate it like this:

Today, I bought some ice cream and topped it with chocolate, bubblegum, and banana and strawberry sauces.

In these examples, we can see that the final comma, the Oxford Comma, disrupts the series of items in the list. We no longer read the list fluidly with all of these items connected, but we read them as separate items enumerated together.

The Oxford Comma can thus be used to better clarify and distinguish between items in a list. When there is no comma, items are directly linked; when the Oxford Comma is used, these items are separated.

Let's use another example.

This morning, five aliens came down from outer space. They were blue, orange, yellow, green and red.

Without the Oxford Comma, all of the listed colours are directly linked, and this sentence implies that the aliens are all multicoloured, that their skin has pigments, perhaps patches, of all of the colours listed above.

Now, let's see the sentence again but, this time, using the Oxford Comma:

This morning, five aliens came down from outer space. They were blue, orange, yellow, green, and red.

Now that we have separated each of the colours with commas, and there are five aliens and five colours, we can assume that each alien was a different one of these colours, rather than all of them being a mixture of all of the colours.

Let's use what we've learned and apply it to a final example using 'or' as well as 'and'.

Five aliens came down from outer space. I'm not sure what colour they were, but I think they were blue, green, yellow and orange or red.

As this sentence stands, it reads as though all of the aliens were a mixture of blue, green and yellow and also either orange or red.

Now, let's add an Oxford Comma into the mix…

Five aliens came down from outer space. I'm not sure what colour they were, but I think they were blue, green, yellow, and orange or red.

The sentence now implies that each alien was a different colour, and the last was either orange or red.

Finally, let's see the Oxford Comma before the 'or' and the effect that this has:

Five aliens came down from outer space. I'm not sure what colour they were, but I think they were blue, green, yellow and orange, or red.

This final sentence now implies that all of the aliens were either a mixture of blue, green, yellow and orange, or they were just all red. This is because red has now been separated from all of the other items in the list, with the Oxford Comma.

It helps in these examples to see commas as either list-makers or separators. Without the Oxford Comma, see all of the items as interrelated and linked; with the Oxford Comma, see the items as distinctly separated.

Again, its usage is disputed amongst grammarians, and so the choice to use it is yours. Whatever you choose, however, must be consistent throughout your work. Personally, I think the distinctions it makes are very useful.