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Why Include The Serial Comma?

By Bob Hesselberth

When we list three, four, or more things in a sentence, (How's that for showing, not telling?) standard English rules allow the last comma in the series (sometimes referred to as the "Oxford comma") to be optional. The writer may elect either to include it or to leave it out.

There are times when the serial comma is necessary to avoid ambiguity, so why not always use it? Always using it will avoid most ambiguities. If you always use it, you rarely need to think about whether it's necessary.

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1. In a book dedication: To my parents, Ayn Rand and God.

There is ambiguity about the writer's parentage, because "Ayn Rand and God" can be read as in apposition to 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:

2. From a newspaper account of a documentary about Merle Haggard: Among those interviewed were his two ex-wives, Kris Kristofferson and Robert Duvall.

A serial comma following "Kris Kristofferson" would help prevent this sentence from claiming that Kris Kristofferson and Robert Duvall were the ex-wives.

3. Forgetting to use the serial comma can be expensive.

In a Maine labor dispute, 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. As the U.S. appeals judge David J. Barron wrote, "For want of a comma, we have this case."

Serial Comma

In the case known as 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 (a list in which the coordinating conjunction is absent). Truck drivers demanded overtime pay, and 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".

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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."

On the other hand, the inclusion of a serial comma can cause ambiguity. If we modify the above dedication to read, "To my mother, Ayn Rand, and God" it can appear that Ayn Rand is the writer's mother. But because these occasions are rare, your odds of writing unambiguous sentences are better if your default practice is to include the serial comma. Whether you include it or not, always review your sentences for clarity and consider restructuring the sentence.

(For more information on this subject, look up "serial comma" in Wikipedia. You'll find more than you ever wanted to know.)


If you want to read a memoir to remember, you'll find this one loaded with juvenile hi-jinx, incoherent humor, pulse-pounding suspense, and loads of self-aggrandizement: You'll also find the story of starting Spectracom Corporation in my basement and eventually selling it to a venture capital company. Two Shakes of a Lamb's Tail to find it on Amazon. 


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