Quote:
In most house styles, the comma is preferred before the last item in a list: "the first, second, and third chapters." (This is known as the serial comma or the Oxford comma.) Leaving it out — "the first, second and third chapters" — is a habit picked up from journalism. While it saves a teensy bit of space and effort, omitting the final comma runs the risk of suggesting the last two items (in the example above, the second and third chapters) are some sort of special pair. A famous (and perhaps apocryphal?) dedication makes the danger clear: "To my parents, Ayn Rand and God."