Oxford Comma is the final comma in the list of things mentioned in a sentence. In this statement,
I like computer science, maths, and programming.
The comma after the word maths and before the conjunction, and, is considered the Oxford comma. Other commonly used terms that refer to this style are the serial comma, a series comma, or a Harvard comma.
In my writing, before this essay, I had never added a comma on the final element of the conjunction. This topic piqued my interest, and I started doing research on this entity.
The term, Oxford comma, got its name from the Oxford University Press style guide. It was recommended by the Oxford style guide even when many British journals and publications were not recommending it. My first conscious encounter with it was during the diagnostic test. I was not able to correct the sentence by placing a serial comma. I had never considered a statement, with a list of items, wrong if it did not have a serial comma. We always try to infer the meaning from the context. But in fact, as will see shortly, it may not be possible at all times and the reason to include Oxford comma is to reduce ambiguity in the sentence.
The reason we do not notice the lack Oxford comma is, the Associated Press style guide, which many newspapers follow, does not require us to use Oxford comma, and thus, it is often left out. Let's notice an ambiguity when we lack the Oxford comma.
To my parents, Alicia and Steve Jobs.
There is an ambiguity about the writer's parentage here because Alicia and Steve Jobs can be read as in apposition to his parents, leading the reader to believe that writer claims Alicia and Steve Jobs are his parents. Whereas, placing the Oxford comma after Alicia will resolve the ambiguity.
To my parents, Alicia, and Steve Jobs.
It articulates clearly that the writer is referring to 3 separate entities in his dedication. There are cases when inclusion of Oxford comma can make a sentence ambiguous too. For example, this statement:
To my father, Steve Jobs, and Alicia.
The serial comma after my father creates ambiguity about the writer's father because it uses punctuation identical to that utilized for an appositive phrase, suggesting that Steve Jobs is the writer's father. It is unclear whether there are three people (1. my father; 2. Steve jobs; and 3. Alicia) or it is only two (1. Steve Jobs and 2. Alicia. Steve Jobs is writer's father). The common way to disambiguate this sentence is to refer to each entity as a noun. For e.g.
To my father, to Steve Jobs, and Alicia.
Thus, the placement of the comma can significantly affect the meaning of the entire sentence. By appropriately choosing words and with always using Oxford comma, we can write less ambiguous phrases. Also, Oxford comma matches with the spoken cadence of sentences better.
If you need only one reference to remember this concept, then keep this picture in your mind.
One more thing.
Listen to "Weird Al" Yankovic - Word Crimes before you move beyond this page.