Serial comma


The serial comma is a comma placed after the second-to-last term in a list when writing out three or more terms. For example, a list of three countries might be punctuated with the serial comma as "France, Italy, and Spain" or without it 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 its use.
The serial comma is popular in formal writing 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 serial comma, as does The Oxford Style Manual. 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.

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. The serial comma has been used for centuries in a variety of languages, though not necessarily in a uniform or regulated manner.
The serial 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 serial comma as such in his historical account of the Oxford University Press.
Sutcliffe, however, attributed the serial 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 the consistent use of the serial comma are:
  • The comma's use is consistent with the conventional practice of the region.
  • It can resolve ambiguity.
  • Its use is consistent with other means of separating items in a list.
  • Its use is consistent with the spoken rhythm of the sentence, and is especially important for copy meant to be read aloud by a voice actor.
Common arguments against the consistent use of the serial comma are:
  • The comma's omission is consistent with the conventional practice of the region.
  • It can introduce ambiguity.
  • When space is at a premium, it adds redundancy and unnecessary bulk to the text.
Many sources are against both systematic use and systematic avoidance of the serial comma, making recommendations in a more nuanced way as reflected in [|recommendations by style guides].

Ambiguity

Omitting the serial comma may create ambiguity; writers who normally avoid the comma often use one to avoid this. Consider the apocryphal book dedication below:
There is ambiguity about the writer's parentage as "Mother Teresa and the pope" can be read as an appositive phrase renaming of my parents, leading the reader to believe that the writer claims that Mother Teresa and the pope are their parents. A comma before the 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 or no punctuation to introduce or delimit them :
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.
In some circumstances, using the serial comma can create ambiguity. If the book dedication above is changed to
the comma after Mother Teresa creates ambiguity because it can be read as an appositive phrase implying that the writer's mother is Mother Teresa. This leaves it unclear whether this is a list of three entities or of only two entities.
The Times once published an unintentionally humorous description of a Peter Ustinov documentary, noting that "highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector". Again, there is ambiguity as to whether the sentence refers to three distinct entities, or whether Mandela is being described as both a demigod and a dildo collector. The addition of a serial comma would not resolve the issue, as he could still be mistaken for a demigod, although he would be precluded from being a dildo collector.
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. 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 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 would remove the ambiguity:
  • One person
  • * They went to Oregon with Betty, who was a maid and a cook.
  • * They went to Oregon with Betty, both a maid and a cook.
  • * They went to Oregon with Betty.
  • * They went to Oregon with Betty, their maid and cook.
  • Two people
  • * They went to Oregon with Betty and a cook.
  • * They went to Oregon with Betty—a maid—and a cook.
  • * They went to Oregon with Betty, a maid, and with a cook.
  • * They went to Oregon with the maid Betty and a cook.
  • * They went to Oregon with a cook and Betty, a maid.
  • Three people
  • * They went to Oregon with Betty, as well as a maid and a cook.
  • * They went to Oregon with Betty and a maid and a cook.
  • * They went to Oregon with Betty, one maid and a cook.
  • * They went to Oregon with a maid, a cook, and Betty.
  • * They went to Oregon with a maid, a cook and Betty.
  • * ''They went with Betty to Oregon with a maid and a cook.''

    In general

  • The list x, y and z is unambiguous if y and z cannot be read as a renaming of x.
  • Equally, x, y, and z is unambiguous if y cannot be read as a renaming of x.
  • If neither y nor y and z can be read as a renaming of x, then both forms of the list are unambiguous, but if both y and y and z can be read as a renaming of x, then both forms of the list are ambiguous.
  • x and y and z is unambiguous if x and y and y and z cannot both be grouped.
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 English style guides

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 comma, possibly for economy of space. In Australia and Canada, the comma is typically avoided in non-academic publications unless its absence produces ambiguity.
It is important that the serial comma's usage within a document be consistent; inconsistent usage can seem unprofessional.

Mainly American style guides supporting mandatory or typical use

;The United States Government Printing Office's Style Manual
;Wilson Follett's Modern American Usage: A Guide, pp. 397–401:
;The Chicago Manual of Style, 16th edition, paragraph 6.18
;The Elements of Style, Rule 2
;The American Medical Association Manual of Style, 9th edition Chapter 6.2.1
;The Publication Manual of the American Psychological Association, 6th edition Chapter 4.03
;The CSE Manual for Authors, Editors, and Publishers, Section 5.3.3.1
;Garner's Modern English Usage, 4th edition, "Punctuation," § D, "Comma", p. 748
;MLA Style Manual and Guide to Scholarly Publishing, paragraph 3.4.2.b
;AAMT Book of Style for Medical Transcription
;AIP Style Manual, American Institute of Physics, fourth edition, 1990
;Plain English Handbook, Revised Edition, § 483, p. 78

Mainly American style guides opposing typical use

;The New York Times stylebook
;''The AP Stylebook''