Perhaps no mark of punctuation ruffles feathers more than the serial comma (also called series comma, Oxford comma, and Harvard comma). This comma precedes the final item in a list or series, before the word and or or. With the exception of newspapers, most publications use the serial comma, because it helps writers avoid ambiguity. Who would object to unambiguous prose? you might ask. Fair-weather comma users: publications that do not require the serial comma may use it only when misreading results. Proponents of the serial comma, like the MLA, would decry the inconsistency of the use-it-when-you-need-it approach and advocate using the serial comma in all series of three or more items or phrases.
Here’s an example where omitting the serial comma results in ambiguity:
Lia ordered three smoothies: strawberry, peach and mango and pineapple.
Without a serial comma placed after peach or after mango, it isn’t clear if “peach and mango” is one flavor or if “mango and pineapple” is.
Here’s another example:
Sam took his dog for a walk and ran into Deirdre, a friend and his dentist.
As written, the sentence might mean that Deirdre is a friend of Sam’s and also his dentist. But, alternatively, the sentence might mean that Sam met three people, not one: Deirdre, a friend, and his dentist. Without the serial comma, there’s no way to know.
When items in series themselves contain commas, additional punctuation is needed to clarify the items. Consider this sentence:
The invited speakers are the association’s president, the vice president, the councilwoman, Suzette Tanner, and Walter McCarthy, the executive director.
Here, commas aren’t enough to clarify the items in the series: is the councilwoman named Suzette Tanner or are Suzette Tanner and the councilwoman two people? Adding serial semicolons provides clarity:
The invited speakers are the association’s president; the vice president; the councilwoman, Suzette Tanner; and Walter McCarthy, the executive director.
The semicolons make it clear that there are four speakers. To use serial semicolons, place them wherever you would normally place serial commas, to separate like terms. Here’s a more complex example where serial semicolons are needed:
In his report, Mr. McCarthy presented on the annual budget, the plans to hire a director of operations, a chief financial officer, and a human resources assistant, the fund-raising efforts of the development committee, which expects to meet its goal by the end of the fiscal year, the recent accomplishments of the committees on accessibility, research, and sustainability, and the restructuring of the product development team.
The addition of serial semicolons makes clear which items belong together and makes the sentence easier to read:
In his report, Mr. McCarthy presented on the annual budget; the plans to hire a director of operations, a chief financial officer, and a human resources assistant; the fund-raising efforts of the development committee, which expects to meet its goal by the end of the fiscal year; the recent accomplishments of the committees on accessibility, research, and sustainability; and the restructuring of the product development team.
Still not convinced of the importance of the serial comma? A court ruling in a labor dispute earlier this year upped the stakes of this normally low-profile punctuation mark. The decision centered on the absence of a serial comma in a Maine state law, which could end up costing a company millions of dollars in overtime pay to truck drivers. An appeals court agreed with the drivers that the missing comma rendered the interpretation of the law ambiguous, and the lawyer representing the drivers credited the absence of the comma with winning them the case (Victor). A win for the drivers and for champions of the serial comma!
Victor, Daniel. “Lack of Oxford Comma Could Cost Maine Company Millions in Overtime Dispute.” The New York Times, 16 Mar. 2017, www.nytimes.com/2017/03/16/us/oxford-comma-lawsuit.html.