The Oxford comma is the comma placed before the conjunction at the end of a list of things. For example, in “the flag was red, white, and blue”, the Oxford comma would be the one appearing before “and”. Proponents of the Oxford comma say it’s necessary for removing ambiguity in sentences.

Regardless of the order, a proper noun and a common noun would be next to each other in a list, and an Oxford comma would allow readers to mistake one as a clarification of the previous noun. Another reason to skip the Oxford comma is to save time, both for the writer and reader.

When we have a list of three or more items, we use a comma to split the items in the list. Listing commas can separate lists of nouns, verbs, adjectives, dependent clauses, or even complete sentences.

Most modern writing guidebooks like Garner’s Modern American Usage and The Chicago Manual of Style say you should always use the serial comma before “and.” The reasoning behind this is to avoid ambiguity and confusion.

Its name comes from the Oxford University Press (OUP), where for over a century it has been standard in the Oxford Style Manual. Sometimes it’s called a ‘serial comma’, and less frequently a ‘Harvard comma’ (from Harvard University Press).

The Oxford (or serial) comma is the final comma in a list of things. For example: Please bring me a pencil, eraser, and notebook. The Oxford comma comes right after eraser. Use of the Oxford comma is stylistic, meaning that some style guides demand its use while others don’t.

What is the Difference Between an Oxford Comma and a Regular Comma? Technically, the Oxford comma is no different since it’s still a comma. However, unlike the regular comma that holds grammatical significance, the use of an Oxford or serial comma is a stylistic choice.

Technically, it’s grammatically optional in American English. However, depending on the list you are writing out, omitting it can lead to some confusion.

Commas should be used when three or more items in a series are listed. A comma should be placed between each of the three items (it is also acceptable to leave out the comma between the second-to-last item and the last item in the series). Items in the series may consist of a word, clause, or phrase.

Lawyers should use the Oxford comma to help avoid ambiguity. Three ambiguities may arise without this comma: Whether the two final items in a list are one combined element or separate.

In its own text, the guide by Cambridge omits serial commas; Oxford’s retains them. So for British English, use serial commas or omit them, but do so consistently.