Commas Part 3: Interrupters

Often, you have a word, a phrase, or a clause that interrupts the flow of the sentence. Sometimes you use commas around such an interrupter. If the element is added information and you don’t need it for the meaning of the sentence to be clear, use commas around it. Such a word, phrase, or clause is called “nonrestrictive,” or “nonessential.”  If the information is necessary for the meaning of the sentence, do not use commas. Such information is called “restrictive,” or “essential.” At times, it might be difficult to ascertain whether something is essential or not. Sometimes you can tell by using the “would I pause?” test, but not always.

 

Here are some nonessential interrupters:

I know, by the way, all about your little secret.

This story is, for your information, good enough to publish.

My neighbor two doors down, who recently moved in, just left for Italy. (You already know which neighbor: the one two doors down.)

My brother’s math teacher, Mr. Quinn, is a really easy grader. (Presumably, he has only one math teacher.)

My birthday cake, chocolate with lemon icing, was delicious! (We are assuming it was your only birthday cake, so we don’t need to distinguish it from other cakes.)

 

Which one of these is correct?

Joe’s mother, Abigail, is wearing the same dress as I am.

Joe’s mother Abigail is wearing the same dress as I am. 

If you said “the first one,” you are probably correct. Can you tell the difference in presumed meaning?

The first sentence treated Abigail as unnecessary, added information. The second sentence assumes that Abigail is necessary to the meaning of the sentence. What is the difference, and why is the first sentence most likely better?

We can assume that Joe has only one mother. Therefore, we don’t really need to use her name. Using her name implies we are specifying which mother out of multiple mothers. 

 

So….which one of these is correct?

My brother, Paul, is the tallest person in the family.

My brother Paul is the tallest person in the family.

Either one could be correct, depending on the makeup of the family. The first sentence, which treats Paul as added information, assumes that you have only one brother so you don’t need to name him. The second sentence, which treats Paul as necessary, implies that you have more than one brother, so you need to specify which brother you are talking about.

 

Here are some essential interrupters: no comma.

My neighbor across the street has a beautiful garden. (Which neighbor? Oh, the one across the street, not the one next door.)

The pizza with the anchovies is nearly gone. (Which pizza? The one with the anchovies, not the one with pepperoni.)

All the teachers who have been at the school for more than 20 years are being honored.  (Not all the teachers, but just the ones who have been at the school for more than 20 years.)

All the teachers, who have been at the school for more than 20 years, are being honored. (This could mean all the teachers have been at the school for over 20 years. It could also mean you know which group of teachers is being referred to, and you are mentioning they have all been at the school for more than 20 years. 

 

Usually participial phrases that interrupt a sentence are set off with commas:

My dog, gnawing on a big bone, must be hungry.

The principal, marching into the classroom with a red face, must be very angry.

I don’t know how the cat, walking along the top of the fence, doesn’t fall down.

Often a descriptive phrase is set off with commas:

This coffee, much too strong for me, needs a lot of sugar.

The sky, usually beautiful at sunset, was dark and foreboding today.

My history paper, due next Tuesday, will likely be late. 

 

Stay tuned for a guest post about Ten Grammar Mistakes ESL Students Make next week — followed by more in the comma series — for you comma lovers (or haters).