Should I put a comma before the last item in a list?
I would like crackers, cheese and some soda.
I would like crackers, cheese, and some soda.
Using a comma before the last item in a list is known as the Oxford Comma, sometimes the Serial Comma. It is used before conjunctions in a list like this with three or more items. Its use is purely written style and optional. It is more common in America outside journalism, and much less common in other English speaking areas of the world. There are arguments for and against which usually come down to comprehension. Wikipedia quotes these ambiguities:
To my parents, Mother Teresa and the Pope.
To my parents, Mother Teresa, and the Pope.
Also on that wiki page you can find lots of links to certain style guides. Comma use is something of a grey area though, and everyone has his own style. Pick what reduces ambiguity.
Language log has an interesting article on how reading comprehension can be improved with comma use, including this type.
Not using that comma can lead to factual errors, as in the apocryphal book foreplate:
The highest-scoring answer to this question asserts that using the serial comma is "purely [a matter of] written style and [therefore] optional." To demonstrate that neither including serial commas nor omitting serial commas leads in all cases to ambiguity-free sentences, he cites a familiar pair of amusingly misinterpretable dedications:
To my parents, Ayn Rand and God.
To my mother, Ayn Rand, and God.
Arguably the writer of the first example may be referring to four personages (two parents, a mortal author, and a Deity) or to two (two parents, one of whom who happens to be a mortal author and the other of whom happens to be a Deity). Likewise, the writer of the second example might be referring to three personages (one parent, one mortal author, and one Deity) or to two (a parent who happens to be a mortal author, and a Deity). The inference we seem to be invited to draw from these examples is that you can't win under either system of punctuation, so objectively it doesn't matter which one you choose: The two systems are equally unsatisfactory and equally susceptible to confusion. I think that this implicit argument misrepresents the case to a significant extent.
It is certainly true that each system fails in one of the examples above. But in other situations, the serial-comma system has an undeniable advantage over a strict no-serial-comma system. This fact is obvious from the advice that The Associated Press Stylebook (2002) offers publications that follow its (usually no-serial-comma) style. As I noted a year ago in my answer to a post about Serial commas in quotations, AP makes two important exceptions to its normal no-serial-comma rule:
Put a comma before the concluding conjunction in a series, however, if an integral element of the series requires a conjunction: I had orange juice, toast, and ham and eggs for breakfast.
Use a comma also before the concluding conjunction in a complex series of phrases: 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 mental attitude.
Establishing these two exceptions amounts to temporarily adopting the serial comma system in two specific situations where a strict no-serial-comma rule might yield ambiguous or difficult-to-follow sentences and where the serial-comma system has no countervailing disadvantages.
In short, the strict serial-comma system runs into ambiguity problems with certain appositive constructions, while the strict no-serial-comma system runs into ambiguity problems with certain appositive constructions, with certain series that contain one or more integral elements requiring a conjunction (as AP puts it), and with series whose elements are sufficiently complex.
As for the appositive ambiguity that plagues both systems in connection with God and Ayn Rand, I think that reworking the sentence to avoid the problem usually makes more sense than suspending your normal rule for including or excluding serial commas. Under either system of comma use, you can remove any shadow of potential ambiguity—in the more common circumstance where God and Ayn Rand are not your parents—by reframing the dedication as follows:
To my parents, to Ayn Rand and to God.
To my mother, to Ayn Rand, and to God.
I once encountered the following biographical snippet intended for the close of a magazine article:
He currently lives with his wife, a ferret, and a cat who thinks she is a ferret.
Our house style was to use a serial comma, but the author's description of his familial complications suggested that he might be risking a change for the worse in his current living arrangements if his wife (the ferret) got wind of his characterization of her. Retaining the serial comma after ferret clearly wouldn't do, but omitting it wouldn't get us out of the woods either. After all, just as one might describe a person as "a genius and a madman who knows he is a genius," one might (foolishly) refer to one's spouse as "a ferret and a cat who thinks [he or she] is a ferret."
My solution to the problem was to rework the sentence to relieve the overmatched comma (and its stripped-out doppelganger) of the burden of clarifying the relations between the named parties:
He and his wife have two pets: a ferret and a cat who thinks she is a ferret.
Ultimately a writer's best weapon in the struggle against unwanted ambiguity is neither the serial comma nor the lack thereof, but the ability to rephrase to avoid trouble.
The basic question here is about disambiguation. Does the comma give you information that you need in order to fully understand the sentence? If it does, you want to include it. If not, it's not necessary, although it can still be used. It's common in the United States, not so much in the U.K.
In addition to the examples itrekkie listed, you could also consider this:
"I leave all my worldly possessions to my nieces Sarah, Jane, and Carol." This sentence implies that each niece would receive 1/3 of the estate.
"I leave all my worldly possessions to my nieces Sarah, Jane and Carol." This sentence could be read to imply that Sarah gets 50% of the estate, while Jane and Carol each get 25%.
Sometimes the serial comma is necessary to delineate the final two items in the list when the final item is a compound item (containing the word "and").
My favorite drinks are Long Island Iced Tea, Bloody Mary, vodka, and Jack and Coke.
My favorite drinks are Long Island Iced Tea, Bloody Mary, vodka and Jack and Coke.
I'm not sure if anyone really drinks a vodka+Jack+Coke, but it could happen!
In my book Rules for Writers - Diana Hacker
When three or more items are presented in a series, those items should be separated from one another with commas. Items in a series may be single words, phrases, or clauses. Although some writers view the comma between the last two items as optional, most experts agree that it is better to put it in because its omission can result in ambiguity or misreading.
She provides an example:
The activities include a search for lost treasure, dubious financial dealings, much discussion of ancient heresies[,] and midnight orgies.
Without the comma this sentence is easily misread. The people seem to be discussing orgies, not having them. The comma makes it clear that midnight orgies is a separate item in the series.
The comma before the "and" is called an Oxford comma or a serial comma. Despite being called an Oxford comma, Brits don't commonly use it.
Opinions vary among writers and editors on the usage or avoidance of the serial comma. In American English, the serial comma is standard in most non-journalistic writing, which typically follows the Chicago Manual of Style. Journalists, however, usually follow the AP Stylebook, which advises against it. It is less often used in British English. In many languages (e.g. French, German, Italian, Polish, Spanish), the serial comma is not the norm; it may even go against punctuation rules, but it may be recommended in some cases to avoid ambiguity or to aid prosody.
I, too, was taught never to use a Serial comma, but it is by no means solely an American thing to add the extra punctuation — the extra comma is actually frequently known as the Oxford comma, because it is the house style of Oxford University Press, one of the oldest and most influential publishers in the world.
I agree with Wikipedia on this issue — opinions on the use of the serial comma "vary among writers and editors."
In American English, the serial comma is standard in most non-journalistic writing, which typically follows the Chicago Manual of Style. Journalists, however, usually follow the AP Stylebook, which advises against it. It is less often used in British English. In many languages (e.g. French, German, Italian, Polish, Spanish), the serial comma is not the norm; it may even go against punctuation rules, but it may be recommended in some cases to avoid ambiguity or to aid prosody.
The latter example is known as the serial comma, Harvard comma or Oxford comma, these last two names coming from the style guides of Harvard University Press and Oxford University Press insisting upon it.
Opinion varies. If you are writing to a style guide then you should follow the rules placed upon you (Chicago Manual of Style insists upon it, while the Associated Press Stylebook advises against).
It's more common in America than Britain, but both styles are found throughout the English-speaking world.
There are a few cases where it can avoid ambiguity, but otherwise if you don't have a style-guide dictating on the matter, it's up to you.
We use commas to separate items in a series or list. In British English, a comma is not usually used with and between the last two items unless these are long.
I went to Spain, Italy, Switzerland, Austria and Germany.
(US...Austria, and Germany).
I spent yesterday playing cricket, listening to jazz records, and talking about the meaning of life.
(from Michael Swan's PEU)
The 'Oxford comma' is an optional comma before the word 'and' at the end of a list:
We sell books, videos, and magazines. Oxford comma It's known as the Oxford comma because it was traditionally used by printers, readers, and editors at Oxford University Press. Not all writers and publishers use it, but it can clarify the meaning of a sentence when the items in a list are not single words:
These items are available in black and white, red and yellow, and blue and green.
The Oxford comma is also known as the 'serial comma'. (From OxfordDictionaries.com)
- Where more than two words or phrases or groupings occur together in a sequence, a comma should precede the and. This is the so- called 'Oxford comma'.
The 'Oxford comma' is frequently, but in my view unwisely, omitted by many other publishers. Their preference is to omit it as a general rule (e.g. tea, scones and cake) but to insert it if there is a danger of misunderstanding (tea, bread and butter, and cake—examples from J. McDermott, 1990).
(From New Fowler's Modern English Usage)
This is known as the serial comma. There is a whole discussion in Wikipedia about its usage in various style guides.
The preferred style in the US is to always use the serial comma; elsewhere, it is less common, particularly in the UK. Choosing not to use the serial comma has little benefit other than reducing the number of marks on the page, whereas its omission has two notable drawbacks.
As ever, the priority is consistency.
In styles that use a serial comma, an exception is made before an ampersand, which is a display element, not a word. When an ampersand is used in a list, the serial comma is omitted because it's visually jarring.
If the comma before an ampersand is needed to avoid ambiguity, the best thing to do is change the ampersand back to the word "and."
Urban legend has tried to teach people that the comma before the "and" in this situation is optional, but it isn't. The legend of removing the comma originated back in manual typesetting days when newspaper print space was at a premium, and that particular comma became expendable. That's the origin of this errant "omission rule" that, I believe, has made it into the AP style book.
Think about this for a minute: what would it actually mean for using the comma here to be "right" or "wrong" and why would your teacher be the authority on this? Did your teacher have special exclusive access to a special 11th commandment on comma usage issued by God?
What you're dealing with is a stylistic preference. There's no "right" and "wrong" here. What do you prefer or feel is more sensible (easier to read etc)? Or, where applicable, what does your editor/publisher's in-house style guide prefer to you to do in these cases?
If you are making the decision, that competing factors you might want to weigh up:
Which of these factors (and any others you might think of) do you feel wins out overall?