 It goes by many names, the Oxford comma, the Harvard comma, or the final serial comma. And if I had written down that last sentence, I might have used one. Most people know that when you have a list or series, the convention is to separate each item with a comma. We call those serial commas, and many people have been taught the last one is optional. But that's not exactly true. The actual rule is that when we have a list of items, we always need a conjunction between them, a connecting word. That's true whether the items are nouns, or verbs, or adjectives, or anything else. Or, or, or. That's one conjunction commonly used with lists. It signals and completes and clarifies the construction, and, and, and. That's the other common conjunction in lists. Well, when we use serial commas, they just take the place of the conjunctions. They operate as stand-ins, but before the last item, we usually state the conjunction so we don't need a stand-in. That was the traditional thinking, and so the final comma was traditionally left out. That's why America's 1776 Declaration of Independence reads, life, liberty, and the pursuit of happiness. No comma after liberty. The big shift to this thinking came in 1905 when a printer named Horace Hart updated his style guide for Oxford University Press, requiring his employees to use a comma before the last item in a series. The prestige of the press and the public availability of the guide made it very influential, and that is, of course, why we call it the Oxford comma today. Do we really need to use it? Well, it depends who you ask. If you were working for Oxford University Press in 1905, you would ask Horace Hart, and the answer would be yes. Ask most other English presses at the time, and the answer would be no. We still have style books like Hart's today, and for publishing writers, they're usually the final authority on grammar. Most of these style books are exactly the same except for a few small details, and one of those details is the Oxford comma. In America, you're required to leave it out if you use the AP style book, like most newspapers. You're required to leave it in if you use the Chicago manual style, like most publishers, or the MLA handbook, like most academic disciplines. If you're writing for school in the United States, MLA is usually standard unless your teacher says otherwise. So is it optional? Not really. There are just different requirements from different authorities that you heed in different situations. Is it better to include it? Overall, Americans tend to say yes, and the British tend to say no. The truth is there are arguments for logic and clarity on both sides, and both sides tend to get pretty passionate about it. So what's your opinion? Do you like including the Oxford comma or not? Let us know in the comments section and tell us your reasons.