And now for something really controversial: The serial comma

Life, Liberty, and the Serial Comma

Life, Liberty, and the Serial Comma (Photo credit: MBIMOTMOG)

Today I’m going to take on a really controversial subject:

The serial comma

I’m for it.

I’m speaking about the comma before the “and” that precedes the last item in a series, such as “red, white, and blue,” or “oats, peas, beans, and barley.”

I was taught in school to put it in and so were my sons. Lately, however, there seems to be a trend to leave it out, and this is shaping up to be one of the major punctuational battles of our times.  Seriously.  If you make the mistake of bringing the subject up in any group of serious writers (or editors), you’re likely to find that people start taking sides and the temperature begins to rise.

So what’s the big deal?

The argument for omitting that last comma goes (I believe) like this:  Since you have the “and” there, what do you need the comma for?  In other words, the claim is that the comma is redundant.

The problem with this argument is that logically commas separate things while “and” joins things together, which means that if you leave that last comma out, logically you’re connecting the last two items of the series while separating them from all the other items. It would make more sense to omit the “and” and keep the comma if you don’t think you need them both, except, of course, that we’re so used to the “and” being there.

Possibly the” and” at the end of the series is the last vestige of a more cumbersome construction: “red, and white, and blue.”  After all, the items in the series are linked in the sense that they all belong in the series, even while they are also each separate and distinct from each other. In practical terms, the “and” gives the reader (or listener) a little heads-up that the end of the series is at hand.  It says, “okay, you can stop making your little mental list after this next item and prepare yourself for a change of direction.”

If logic were the only casualty of serial comma omission it might not be worth getting up in arms about. The trouble is, clarity can also take a hit. The comma represents a pause. When you’re speaking, it’s the pause that separates the items in a series in your listener’s perception. And when speaking, you do pause before the “and,” whether you’re aware of it or not. You do it instinctively – and you do it for clarity. If you didn’t pause, you’d make it sound as if the last two items were parts of a single item, like “peanut butter and jelly” (one item) – which in not the same as “peanut butter, and jelly” (two items), or the same as “peanut, butter, and jelly” (three items).  (Say each of those aloud and listen to the difference.)

(You punctuate your speech. Why would you not punctuate your writing?)

Confusion is unlikely in a short, familiar list like, “red, white and blue.” Everyone knows these are the three colors of the American flag. (And there’s no such thing as a “white and blue.”)  But confusion can occur when the items are not familiar, when one or more of the items contains an internal “and,” or when the items are long phrases so that the nature of the series is not immediately obvious.

To illustrate the ambiguity that can arise when items contain internal “ands,” take this example of a hypothetical list of menu options at an ice cream parlor:

 “The choice of toppings includes strawberries and sliced bananas, chocolate chips, sugar sprinkles and peanuts and chocolate sauce.”

So strawberries and bananas apparently come together, and chocolate chips is a stand-alone. But do the sugar sprinkles come with the peanuts, or do the peanuts come with the chocolate sauce? You can’t tell because the missing serial comma could come either after the word “sprinkles” or after the word “peanuts.” This is, of course, a rather trivial example (unless you happen to be allergic to peanuts). You could always ask for clarification, and in all probability the person behind the counter in any real ice cream parlor would give you whatever combination you wanted. I cooked up this example to make a point, and hopefully you can imagine a less contrived and less trivial example.

The point is that when you write something, your intention is presumably to communicate. If your attempt to communicate requires further clarification, you have failed.

To illustrate clarity issues arising from sentence complexity and lack of familiarity of terms, consider the following example drawn from a recent grant announcement posted by the National Institutes of Health. (In which the writer very sensibly does not omit the serial commas):

National Heart, Lung, and Blood Institute (NHLBI) invites applications to develop multidisciplinary career development programs that will equip new MD and PhD (or equivalent) investigators with the knowledge and skills to apply pan-omics and integrated approaches to elucidating genomic and molecular bases of lung disease, including heterogeneity, key regulatory networks, and relevant disease biomarkers, with the goal of advancing understanding of lung disease pathobiology and lung disease personalized medicine applications.


The passage contains two three-item lists.  Did you spot the two serial commas?  One is after the first occurrence of the word “lung” and the other is after “networks.” If the first one were missing it probably wouldn’t trip up most readers because we easily understand that “lung” and “blood” are separate things. But removing the second would make “key regulatory networks” and “relevant disease biomarkers” run together as if they were potentially a single item.  And for all most of us know, they might be. It wouldn’t be until we saw that the comma after “biomarkers” is followed by “with” that we would realize we must have come to the end of the series. Then we would probably have to go back to re-read the sentence so we could figure out what the list of items was intended to be.

Whenever your readers have to go back over a sentence to figure out what you meant, you just flunked Clarity 101.

This is why most technical or scientific writers tend to favor the use of the serial comma. It really helps in long complex sentences. Using it may not always resolve all possible ambiguities, but it never makes things worse.

One final point:

Authorities who advocate omitting the serial comma will often qualify their stance by saying, “unless required for clarity,” which amounts to advocating inconsistency. It means the poor reader never knows what to expect – especially since writers notoriously tend to believe they were clear simply because they know what they were trying to say. It means the writer has to pause to consider possible ambiguity every time he or she composes a list. This requires thoughtful attention to detail, accurate perception, and sound judgment. And can we really expect such traits in a person who would under any circumstances consider omitting a useful piece of punctuation?

Honestly, isn’t it easier and more reliable to simply make a habit of putting in the comma?

Come on, guys; it’s one little keystroke. You can do it!

So where do you stand on this burning issue? Did I put you to sleep in the second paragraph? Are you at this moment cudgeling your brain to come up with something about which you care less?

Dona nobis pacem

Dona Nobis Pacem    Peace…

(A brief poem for this day, Nov 4, 2012)



It’s the word that should begin and end every day of the world, and every thought of every mind in it.


It breathes like a sigh.

It whispers of hope and of the fulfillment of hope.

It sings a song to inspire us all.



Are you with me?