Use a Comma Before a Conjunction

Don’t get distracted by phrases

Here’s a quick comma tip that addresses a mistake I see all the time, one that is easily corrected. It is perhaps a subtle mistake, but still. In addition, there will be a brief, seasonally mandated digression concerning the Grinch. Yes, that “bad banana with a greasy black peel,” that “three-decker sauerkraut and toadstool sandwich with arsenic sauce,” et cetera.

The basic rule

It’s a basic rule of punctuation: Place a comma before a conjunction that joins two independent clauses—even in the presence of an intervening phrase. Most writers easily observe the first part of the rule; the problem lies with the second part about the intervening phrase.

Just to be clear, when I say “conjunctions,” we’re talking about “coordinating” conjunctions, which join clauses of equal rank/importance. (Reminder: the coordinating conjunctions are and, but, and or, and a clause, unlike a phrase, has a subject and a verb—it could stand alone.)

First, let me illustrate the basic rule:

The Grinch hurtled down Mount Crumpit, and he robbed every last Who in Whoville.

“The Grinch hurtled down Mount Crumpit” and “he robbed every last Who in Whoville” are the two independent clauses; and is the conjunction.

Grinch trivia

Time for the aforementioned digression:

Dr. Seuss, aka Theodor Seuss Geisel, grew up in Springfield, MA. Apparently, he looked just a few miles north for inspiration while writing How the Grinch Stole Christmas, basing Mount Crumpit on Mount Tom, and Whoville on the town at its foot, Easthampton (see Wikipedia). I’ve hiked Tom countless times. It’s part of the Holyoke Range, which, now that the leaves are down, I can see through the window of my downtown Northampton apartment as I write.

But back to punctuation.

The reason for the rule

This comma rule prevents ambiguity. Here’s just one example of what can happen if you omit the comma before a coordinating conjunction:

I’m having a dinner in honor of the Grinch and Cindy Lou and I will be cooking all day.

Am I cooking for the Grinch and Cindy Lou? Or is Cindy Lou helping me in the kitchen, maybe cutting green beans with safety scissors?

Don’t let a phrase confuse you

It’s common for writers to misplace this comma when their sentence has a phrase in the middle of it. I’ve observed that the longer the phrase, the more likely the writer will be distracted by it and lose sight of the sentence structure.

Wrong: The Grinch’s heart was the size of a golfball and twice as hard but, when he heard the joyful Who voices drifting up from the valley below, it assumed the proportions and cush of a Super Nerf Ball.

Right: The Grinch’s heart was the size of a golfball and twice as hard, but when he heard the joyful Who voices drifting up from the valley below, it assumed the proportions and cush of a Super Nerf Ball.

The comma still comes before the conjunction. When you pull out the phrase, the sentence structure becomes clear:

The Grinch’s heart was the size of a golfball and twice as hard, but it assumed the proportions and cush of a Super Nerf Ball.

No need to set off the phrase

Note that most of the time you don’t need another comma to set off the beginning of the intervening phrase. The following sentence isn’t wrong, per se, but we can probably agree that the additional comma isn’t doing it a service:

The Grinch’s heart was the size of a golfball and twice as hard, but, when he heard the joyful Who voices drifting up from the valley below, it assumed the proportions and cush of a Super Nerf Ball.

So there you have it. As I said, subtle. But the point is that good punctuation reinforces sentence structure and thereby helps keep your reader on track; poor punctuation opens the way for miscommunication.

Happy holidays, whatever you celebrate. And if you don’t celebrate anything (which can be a wonderful way to preclude the holiday blues), may your heart nevertheless feel big and glad. Maybe I’ll see you on Mount Crumpit, where, looking out over the valley on a clear day in the company of my beloved, my own heart has been known to release its cares and expand almost as much as the Grinch’s.