The serial comma (also referred to as the series comma, Oxford comma, or Harvard comma ) is a comma placed after the second-to-last term in a list (just before the conjunction) when writing out three or more terms. For example, a list of three countries might be punctuated without the serial comma as "France, Italy and Spain" or with the serial comma as "France, Italy, and Spain". The serial comma can help avoid ambiguity in some situations, but can also create it in others. There is no universally-accepted standard for when to use the Oxford comma. The Oxford comma is popular in formal writing (such as in academic, literary, and legal contexts) but is usually omitted in journalism as a way to save space. Its popularity in informal and semi-formal writing depends on the variety of English; it is usually excluded in British English, while in American English it is common and often considered mandatory outside journalism. Academic and legal style guides such as the APA style, The Chicago Manual of Style, Garner's Modern American Usage, Strunk and White's The Elements of Style, and the U.S. Government Printing Office Style Manual either recommend or require the Oxford comma, as does The Oxford Style Manual (hence the name "Oxford comma"). Newspaper stylebooks such as the Associated Press Stylebook, The New York Times Style Book, and The Canadian Press stylebook typically recommend against it. Most British style guides do not require it, with The Economist Style Guide noting most British writers use it only to avoid ambiguity. While many sources provide default recommendations on whether to use the serial comma as a matter of course, most also include exceptions for situations where it is necessary to avoid ambiguity (see ).

History

The comma itself is widely attributed to Aldus Manutius, a 15th-century Italian printer who used a mark—now recognized as a comma—to separate words. Etymologically, the word comma, which became widely used to describe Manutius's mark, comes from the Greek κόμμα lit. 'to cut off'. The Oxford comma has been used for centuries in a variety of languages, though not necessarily in a uniform or regulated manner. The Oxford comma is most often attributed to Horace Hart, the printer and controller of the Oxford University Press from 1893 to 1915. Hart wrote the eponymous Hart's Rules for Compositors and Readers in 1905 as a style guide for the employees working at the press. The guide called for the use of the serial comma, but the punctuation mark had no distinct name until 1978, when Peter Sutcliffe referred to the Oxford comma as such in his historical account of the Oxford University Press. Sutcliffe, however, attributed the Oxford comma not to Horace Hart but to F. Howard Collins, who mentioned it in his 1905 book, Author & Printer: A Guide for Authors, Editors, Printers, Correctors of the Press, Compositors, and Typists.

Arguments for and against

Common arguments for consistent use of the serial comma: Common arguments against consistent use of the serial comma: Many sources are against both systematic use and systematic avoidance of the serial comma, making recommendations in a more nuanced way (see Recommendations by style guides and subsequent sections).

Ambiguity

Omitting the serial comma may create ambiguity. Writers who normally avoid the serial comma often use one when it avoids ambiguity. Consider this apocryphal book dedication: There is ambiguity about the writer's parentage because "Ayn Rand and God" can be read as a renaming of my parents, leading the reader to believe that the writer claims that Ayn Rand and God are the parents. A comma before and removes the ambiguity: Nevertheless, lists can also be written in other ways that eliminate the ambiguity without introducing the serial comma, such as by changing the word order or by using other punctuation, or none, to introduce or delimit them (though the emphasis may thereby be changed): An example collected by Nielsen Hayden was found in a newspaper account of a documentary about Merle Haggard: A serial comma following "Kris Kristofferson" would help prevent this being understood as Kris Kristofferson and Robert Duvall being the ex-wives in question. Another example: It is unclear whether the eggs are being grouped with the bacon or the toast. Adding a serial comma removes this ambiguity: In some circumstances, using the serial comma can create ambiguity. If the book dedication above is changed to the serial comma after Ayn Rand creates ambiguity about the writer's mother because it uses punctuation identical to that used for an appositive phrase, leaving it unclear whether this is a list of three entities (1, my mother; 2, Ayn Rand; and 3, God) or of only two entities (1, my mother, who is Ayn Rand; and 2, God). Or consider This is ambiguous because it is unclear whether "a maid" is an appositive renaming of Betty or the second in a list of three people. On the other hand, removing the final comma: leaves the possibility that Betty is both a maid and a cook (with "a maid and a cook" read as an appositive phrase ). So in this case neither the serial-comma style nor the no-serial-comma style resolves the ambiguity. A writer who intends a list of three distinct people (Betty, maid, cook) may create an ambiguous sentence, regardless of whether the serial comma is adopted. Furthermore, if the reader is unaware of which convention is being used, both styles can be ambiguous in cases such as this. These forms (among others) would remove the ambiguity:

In general

Ambiguities can often be resolved by the selective use of semicolons instead of commas when more separation is required. General practice across style guides involves using semicolons when individual items have their own punctuation or coordinating conjunctions, but typically a "serial semicolon" is required.

Recommendations by style guides

Wikipedia's Manual of Style (MOS:SERIAL) leaves use of the serial comma up to the editor so long as individual articles are consistent. Lynne Truss writes: "There are people who embrace the Oxford comma, and people who don't, and I'll just say this: never get between these people when drink has been taken." Omitting a serial comma is often characterized as a journalistic style of writing, as contrasted with a more academic or formal style. Journalists typically do not use the serial comma, possibly for economy of space. In Australia and Canada, the serial comma is typically avoided in non-academic publications unless its absence produces ambiguity. It is important that usage within a document be consistent; inconsistent usage can seem unprofessional.

Mainly American style guides supporting mandatory or typical use

Mainly American style guides opposing typical use

Mainly British style guides supporting mandatory or typical use

Mainly British style guides opposing typical use

Mainly British style guides that consider it generally unnecessary but discretionary

Australian style guides opposing typical use

Canadian style guides opposing typical use

Individual disputes

Maine labor dispute

In the U.S. state of Maine, the lack of a serial comma became the deciding factor in a $13 million lawsuit filed in 2014 that was eventually settled for $5 million in 2017. The U.S. appeals judge David J. Barron wrote, "For want of a comma, we have this case." In O'Connor v. Oakhurst Dairy, a federal court of appeals was required to interpret a statute under which the "canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution" of certain goods were activities exempted from the general requirement of overtime pay. The question was whether this list included the distribution of the goods, or only the packing of the goods for distribution. The lack of a comma suggested one meaning, while the omission of the conjunction or before "packing" and the fact that the Maine Legislative Drafting Manual advised against use of the serial comma suggested another. It said "Although authorities on punctuation may differ, when drafting Maine law or rules, don't use a comma between the penultimate and the last item of a series." In addition to the absence of a comma, the fact that the word chosen was "distribution" rather than "distributing" was also a consideration, as was the question of whether it would be reasonable to consider the list to be an asyndetic list. Truck drivers demanded overtime pay; the defense conceded that the expression was ambiguous but said it should be interpreted as exempting distribution activity from overtime pay. The district court agreed with the defense and held that "distribution" was an exempt activity. On appeal, however, the First Circuit decided that the sentence was ambiguous and "because, under Maine law, ambiguities in the state's wage and hour laws must be construed liberally in order to accomplish their remedial purpose", adopted the drivers' narrower reading of the exemption and ruled that those who distributed the goods were entitled to overtime pay. Oakhurst Dairy settled the case by paying $5 million to the drivers, and the phrase in the law in question was later changed to use serial semicolons and "distributing" – resulting in "canning; processing; preserving; freezing; drying; marketing; storing; packing for shipment; or distributing". The opinion in the case said that 43 of the 50 U.S. states had mandated the use of a serial comma and that both chambers of the federal congress had warned against omitting it, in the words of the U.S. House Legislative Counsel's Manual on Drafting Style, "to prevent any misreading that the last item is part of the preceding one"; only seven states "either do not require or expressly prohibited the use of the serial comma".

British 50p Brexit coin

In 2020 a commemorative 50p coin was brought into circulation in the United Kingdom to mark "Brexit day", January 31, 2020, minted with the phrase "Peace, prosperity and friendship with all nations". English novelist Philip Pullman and others criticized the omission of the Oxford comma, while others said it was an Americanism and not required in this instance.