Nice or Necessary? Commas and Interrupters
by Trista Cornelius
In last month’s column “Dashes, Parentheses, Commas (Which Goes Where – and When?),” I tackled the issue of how to use commas, dashes and parentheses to separate interrupting material from the rest of a sentence. I made the point that dashes are shouts, commas are conversations, parentheses are whispers; and I suggested that your choice of punctuation mark can impact the tone and rhythm of a sentence.
As I promised, this month we’ll look at commas more carefully. Sometimes you need commas around interrupting material; other times, you don’t.
Here’s the rule: If the interrupting material is essential to the meaning of a sentence, you do not use commas. If it’s nonessential, you do use commas.
But what do essential and nonessential mean?
Basically, if information can be lifted out of the sentence and the meaning of the sentence is still clear, it is nice-to-know, but not essential. Nonessential material needs commas around it. Imagine a little grammar helicopter attaching cables to the two commas around the nonessential material and lifting it out; the sentence still works without the interrupting material.
Monique Landers, who drives a behemoth-sized Cadillac, dented Octavia’s blue Porsche.
The interrupting material – who drives a behemoth-sized Cadillac – is nonessential because the material simply adds information. If you take that phrase out of the sentence, it’s still clear who dented Octavia’s car.
On the other hand, essential material is important to the meaning of the sentence and commas should not be used. For example:
The woman driving the Cadillac dented Octavia’s blue Porsche.
The interrupting material – driving the Cadillac – is essential because it clarifies the meaning of the sentence. It’s not any woman who dented one of Octavia’s precious cars; it was the woman driving the Cadillac. Since that’s essential for the reader to know, no commas are used. (No cables for the grammar helicopter to lift the information out the sentence!)
Another comma challenge
Here’s another example you might see and use frequently. Let’s say you’re introducing your spouse. Current culture is monogamous, meaning if someone is married, they are married to only one person. So, if you include the person’s name, it would be nonessential and need commas:
Octavia invited us to her annual party. This is my wife, Priscilla, she said.
Here, Priscilla is another word for wife. You can lift Priscilla out of the sentence and it’s still clear whom Octavia is introducing.
Now, say Octavia is introducing a particular friend, but she has more than one friend.
The sentence would be punctuated like this:
Octavia’s friend Emma Jean tends to twelve Dachsunds each day while the owners go to work.
Here, it’s clear that Emma Jean is the friend who tends Dachsunds, but not Octavia’s only friend. What if, however, Emma Jean is Octavia’s one and only best friend? A sentence indicating that would look like this:
Octavia’s best friend, Emma Jean, makes homemade dog treats every Sunday evening to prepare for the week ahead.
Here, Emma Jean means the same thing as best friend. Her name can be taken out of the sentence and it’s still clear who is making the dog treats.
So as a writer, you have decisions to make: If interrupting material in a sentence is essential, it does not need commas around it; it’s vital to the meaning of the sentence. If it’s simply a nice-to-know detail that can be removed without loss of meaning, it’s nonessential and commas are needed.
Sounds simple in theory. Now put the theory to work. Post examples or questions about this or other topics here, and I’ll get back to you.
This is the eleventh in a series of practical grammar tips every writer needs to know by Trista Cornelius, English Instructor, Clackamas Community College. She’s both the best and worst person to share these tips with you. Best because she’s made all the mistakes herself and learned the hard way. Worst? Same reason!