The use of the Oxford comma is a matter of style, and there is no hard and fast rule about when it should be used. However, there are some general guidelines that can be followed. For example, the Oxford comma is always used when the items in the list are long or complex. It is also used when the items in the list are of different types.
There are some people who argue that the Oxford comma is unnecessary and that it clutters up writing. However, there are also many people who believe that the Oxford comma is essential for clarity.
The debate over the Oxford comma has been going on for centuries. In 1905, the American writer Ambrose Bierce wrote an essay in which he argued that the Oxford comma was "a needless and ridiculous excrescence." However, the Oxford comma has continued to be used by many writers, including some of the most famous writers in English literature.
Today, the Oxford comma is still used by many writers, although its use is not universal. Some style guides, such as the Chicago Manual of Style, require the use of the Oxford comma, while others, such as the AP Stylebook, do not.
Ultimately, the decision of whether or not to use the Oxford comma is up to the writer. There is no right or wrong answer, and it is simply a matter of personal preference. However, it is important to be consistent in your use of the Oxford comma, and to follow the style guide that you are using.
Here are some examples of how the Oxford comma can be used:
I invited Mary, my sister, and John to dinner.
I invited Mary, my sister, and John to dinner.