Commas are punctuation marks that perhaps cause the most trouble for many writers. The comma is used to separate things, ideas, or thoughts in a sentence. Some writers use too many, and some don't use enough.
The series comma, sometimes called the serial comma, or the Oxford or Harvard comma, is the comma that appears just before the "and" or "or" in a series. For example, in the sentence "John likes apples, oranges, and pears.", the comma after the word "oranges" is the series comma.
Some schools of thought believe that the series comma is unnecessary, while others will insist it be used. For example, news agencies generally follow AP style guidelines and do not use the series comma.
Many American businesses follow the Chicago, APA, or other style guidelines, where the series comma is recommended. Again, whichever rule you use, be consistent in your usage.
Janie Sullivan, MBA, MAEd, has been teaching adult learners for over 20 years. She has taught online over 15 years, specializing in writing, communications, and small business applications. Janie directs the Center for Writing Excellence where she offers writing, editing, and formatting services for writers. She has been published in several newspapers and magazines as well as multiple online sites. She teaches communication, business strategy, leadership, and management courses. Janie has published a book "Develop and Deliver an Online Class." This is the third book she has written about writing and teaching online. She also has published a novel and an anthology of short stories.