Note that a serial comma is generally not used when only two parallel items are connected by a conjunction: faith and charity.
Though the AP Stylebook is a notable exception (see Examples and Observations, below), most American style guides recommend using the serial comma for the sake of clarity and consistency. In contrast, most British style guides discourage use of the serial comma unless the items in the series would be confusing without it.
As Miller and Taylor say in The Punctuation Handbook (1989), "Nothing is gained by omitting the final comma in a list, while clarity can be lost in some cases through misreading."
Examples and Observations:
- "Most book and academic editors, using style guides like the Chicago Manual of Style, will publish sentences like this: The candidate promised lower taxes, higher spending, and universal happiness. Most newspapers would print the sentence like this: The candidate promised lower taxes, higher spending and universal happiness. Note that there's no comma before the 'and.' . . .
"There are a few cases, however, where we have to make an exception for clarity. For example: The candidate promised lower taxes, higher spending, and ice cream and cake. Without a comma after 'spending,' the sentence would be a jumble."
(Philip B. Corbett, "Talk to the Newsroom." The New York Times, October 29, 2007)
- Avoiding Ambiguity
The first sentence below doesn't need a comma after "short films." The second sentence, however, would clearly benefit from a comma after the phrase "three female couriers in London."
"After a decade in London, the Bicycle Film Festival rolls back to our screens for another incredible line-up of features, short films and documentaries. Highlights include the ever-popular Urban Bike Shorts, featuring stories about amputee brothers chasing their BMX dreams, three female couriers in London and a postman in Afghanistan."
(Website of The Cycling Solicitors, October 2013)
- Reasons to Use the Serial Comma
"Most newspapers and many other publications don't employ this serial comma, but in more formal writing, such as essays, business letters, and literary works (like this highbrow book), the serial comma is ordinarily retained. We recommend the use of the serial comma because we have found that in many sentences the comma before the conjunction is an aid to clarity, emphasis, and meaning. Consider:
At summer camp I missed my dog, my little brother, the odor of my dad's pipe and my boyfriend. [This sentence misspeaks for itself.]"(Richard Lederer and John Shore, Comma Sense: A Fun-damental Guide to Punctuation. St. Martin's Press, 2005)
- Associated Press Style and the Serial Comma
"[T]he Associated Press Stylebook . . . may have unwittingly contributed to the confusion by saying it's OK to omit the serial comma in a simple list: The flag is red, white and blue. He would nominate Tom, Dick or Harry. But AP style also demands the serial comma when the series is complex, or when the last two items run together ambiguously, or when an item in the list contains a conjunction. Examples:
The main points to consider are whether the athletes are skillful enough to compete, whether they have the stamina to endure the training, and whether they have the proper attitude."The gist of the AP guideline is that we should retain the serial comma in all but the simplest and shortest list, and it does not say that the serial comma is wrong in any case. But that's not the way the guideline has been assimilated. Instead, some writers have concluded--entirely without support--that the serial comma is wrong and should be deleted. But it's not wrong, and no accepted authority would say that it is."
I had orange juice, toast, and ham and eggs for breakfast.
(Paula LaRocque, The Book on Writing: The Ultimate Guide to Writing Well. Marion Street Press, 2003)
- Serial Commas at The New Yorker
"At the New Yorker, one of the first style rules [Harold] Ross established was the serial comma--that is, 'red, white, and blue' instead of 'red, white and blue.' Here he was following his friend Franklin P. Adams, himself a notorious stickler, and Fowler, who argued that since omitting the serial comma sometimes led to confusion as to whether the last two elements in the series are to be taken separately or together, it should always be used. The usage was occasionally objected to as extraneous and stilted, but Ross held firm. 'The serial comma is important because it is almost exclusively the New Yorker's, and is a mildly controversial thing,' he once wrote to Fleischmann. 'But we're right, and all the rest are wrong.'"
(Ben Yagoda, About Town: The New Yorker and the World It Made. Simon and Schuster, 2000)