Pondering Punctuation: Demystifying the Comma, Part Four


One of the surprising side effects of the COVID-19 pandemic has been an increased demand for cybersecurity experts. It seems every time you turn on the TV lately, there are plenty of commercials offering programs to teach jobseekers these skills. Since we’re all online so much now—for work, shopping, and just staying in touch with each other—there’s increased risk of our personal data being stolen.

Have you ever stopped to think about what goes into that personal data? Just what information is essential to identify you as an individual? How about these: your full name; your birthday; credit card numbers; your Social Security number, for you Americans out there—the list is extensive, and even depends on the part of the word you live in.

But then there are other facts about you that, while interesting and maybe even important, are true of many people: that you live in a particular town or city; that you play a particular sport; that you have a dog or cat for a pet, and so on. This type of information doesn’t single you out; you could call it extra information.

In today’s installment of our continuing series on comma usage, let’s take a look at how these types of information—essential and extra—are handled in sentences.


With relative clauses:

A relative clause is a phrase within a sentence that modifies a noun and starts with that, which, or who/whom/whose. Sometimes a relative clause contains information essential to identifying a specific person or thing, but other times it contains extra information. For example:

When we visited the mother dog and her litter, we decided to take the puppy who had a white spot on her chest.

Our puppy, who has a white spot on her chest, loves to play fetch.

Notice how in the first example, the relative clause who had a white spot on her chest is essential for identifying which puppy we selected. If you got rid of that clause, the remaining sentence wouldn’t make any sense: *When we visited the dog and her litter, we decided to take the puppy. This leaves the reader wondering which puppy we picked. (BTW, the asterisk before the sentence means that it’s ungrammatical.)

In the second sentence, however, since we don’t have to single out a particular puppy, you could leave out the relative clause who has a white spot on her chest and the sentence would still make sense: Our puppy loves to play fetch. In this case, the clause who has a white spot on her chest is extra information.

Traditionally, grammarians have called the essential type “restrictive” and the extra type “non-restrictive.” But I’ve never found those terms helpful, so I’m going to stick with these concepts of essential and extra information throughout this post.

Now, on to the role of the comma. Look again at the essential example:

When we visited the mother dog and her litter, we decided to take the puppy who had a white spot on her chest.

Note that there is no comma before who. But in the extra example:

Our puppy, who has a white spot on her chest, loves to play fetch.

There are commas around the clause who has a white spot on her chest. So the rule is: if the relative clause contains essential information, it does not take commas; but if the relative clause contains extra information, it does take commas.

Another way to look at it is that the commas are functioning almost like parentheses—they are signposts that mean “We don’t need this information to identify someone or something.”

One more example:

Every book that Chuck owns is about sports.

The book The Boys of Summer, which Chuck owns, details the history of the early 1950s Brooklyn Dodgers.

If we remove the essential relative clause that Chuck owns from the first sentence, we’d be left with Every book is about sports. And of course that’s not true. Notice that there are no commas, either.

But we can remove the extra relative clause—everything between the commas—from the second and it’s still a true statement: The book The Boys of Summer details the history of the early 1950s Brooklyn Dodgers. The fact that Chuck has a copy of this book is extra information.

You’ve no doubt noticed that in the first sentence the word that starts off the relative clause, but in the second it’s which. You’ll come across some traditional grammars that prescribe using that only with essential clauses, and which only with extra clauses. But this is not actually a hard and fast rule. Native speakers of English tend to automatically use that only with essential clauses, but you can use which with either type. Just go with whichever sounds better to your ear, and then check whether you need to have commas (extra) or not (essential). Chances are that if you naturally used that, it will be an essential clause, which does not need the commas.


With appositives:

Whew! I know that was a lot to absorb. But fortunately this next rule works just like the one for relative clauses.  

First of all, what’s an appositive? It’s a word or phrase which usually follows directly after a noun and provides more information about that noun—for example:

Jason’s wife, Helga, is a German citizen.

Here Helga is an appositive to—more information about—Jason’s wife.

Do you see where we’re going with this? If an appositive provides more information about a noun, sometimes that information is going to be—you guessed it—essential, and other times it’s going to be extra. And the comma rules are exactly the same as with relative clauses: no commas with essential information; commas (again, think parentheses) with extra information.

So why did we use commas in that example? Jason has only one wife, so we don’t need her name to single her out. It’s extra information. But how about this one:

Jenn’s brother Nate came to visit her. 

No commas here—which means that Jenn has more than one brother; Nate is the one who came to visit, and his name is essential in order to pinpoint him. But what if the sentence had been written this way:

Jenn’s brother, Nate, came to visit her. 

At first glance this seems to be the exact same sentence. But check out the commas—this version means that Jenn has only one brother, so his name is extra information.

One more set of examples, this one not so tricky:

Many theater lovers consider Shakespeare’s play Hamlet the greatest drama of all time.

Beethoven’s only opera, Fidelio, is not often performed.

In the first sentence, Hamlet is essential to identify which one of Shakespeare’s plays we’re talking about—so no commas. But in the second sentence, since Beethoven wrote only one opera, the name isn’t essential—it’s extra information.

By now your head is probably spinning—mine certainly was when I first started paying attention to this distinction. And you might even wonder why it matters. I have no answer for that, other than to say that it does: observing the rules and correctly applying (or not applying) the commas will distinguish you as a careful writer who pays attention to detail.

And some good news—this is the most subtle, most difficult application of all of the comma rules. You’ve seen the worst now, so our last installment on the comma will be a piece of cake! I’ll be back soon with those few remaining rules. Until then, as always, look for these principles at work “in the wild,” and practice using them in your own writing. And please feel free to leave any questions below! 

Pondering Punctuation: Demystifying the Comma, Part Three

Image by Sinisa Maric from Pixabay

Everyone knows the value of getting any endeavor off to a good start, whether it’s a new job, a new relationship, or even a blog post. Proverbs about the importance of beginning well abound in many languages. Personally, I’ve always liked the expression “getting off on the right foot,” which is particularly timely now that we can get out more, what with it being summer and with coronavirus restrictions easing.

And of course making a good start also applies to writing. So for today’s installment of our continuing series on commas, let’s look at some rules about correctly using commas when your sentence has an introductory word or phrase. You want the start to be powerful because that’s one of the two strongest positions in the sentence—the other one is the end.

With introductory words:

If you have an introductory word such as an exclamatory Oh or Ah; words like Yes, No, or Well; or if you’re addressing someone by his or her name—all of these need a comma afterwards:

Oh, I love your shoes!

Yes, they look so comfortable.

Jen, where did you buy them?  

red ladies' shoes

With introductory words or short phrases:

Then there are several words or short phrases that, although they’re introductory in nature, tend to pop up in the middle of sentences to clarify something, such as that is, namely, and for example. They usually follow a semicolon or dash, or are enclosed in parentheses. All of them need a comma afterwards:

Many hikers dream of becoming Appalachian Trail thru-hikers; that is, they want to walk the entire trail from start to finish in one trip.

Sports stores usually sell specialized footware—for example, golf shoes and baseball cleats.

My favorite sport (namely, tennis) also requires its own kind of sneakers.   


Now let’s look at two situations in which the introductory phrase is a bit longer: adverbial phrases and participial phrases. Don’t let the grammatical terms put you off; we’ll explain those as we go.

With introductory adverbial phrases:

A single word that’s an adverb modifies a verb, usually adding information such as when the verb happened (such as late), how it happened (slowly), where it happened (there), and so on. An adverbial phrase does the same thing, just with more words—it modifies the verb of the main sentence. Say we had a sentence like this: 

We sat down to eat dinner.

Now we’d like to add an introductory phrase to elaborate more on when we sat down. So we’ll add the phrase and then a comma before the main part of the sentence:

After walking home from the baseball game, we sat down to eat dinner.

If the introductory adverbial phrase is short, the comma may be omitted:

Until 1986 the tennis balls used at Wimbledon were white. (This is clear without the comma after the introductory Until 1986, which specifies when.)

But make sure that if you do leave it out, you don’t make the sentence unclear:

Before eating, their dogs like to go for a walk.

Here’s the incorrect version so you can compare how the reader could get off to a false start if you left out the comma:

Before eating their dogs like to go for a walk.  (Someone’s eating dogs?! Oh, wait, no…) 

Another possibility would be to rewrite this one so that the adverbial phrase is at the end: Their dogs like to go for a walk before eating.  

And finally, there’s just one “don’t” with this rule: do not include a comma if the phrase comes directly before the verb it modifies:

Through the city streets ran all the marathoners.

In this sentence the subject, the actor, is marathoners; they ran (verb) through the city streets (adverbial phrase specifying where).

men's shoe footprints

With introductory participial phrases:

The terms “participle” and “participial” sound like some serious grammar, but they’re just talking about modifiers made from verbs. Participles can be in the present tense, in which case they end in -ing, or past, usually ending in –ed. Let’s start with a main sentence:

Bryan decided it was time to buy new loafers.

Then we want to add an introductory participial phrase to modify when he decided. This will look a lot like the introductory adverbial phrases we just talked about, and once again, the phrase needs a comma after it, before the main part of the sentence:

Noticing the hole in the toe of his shoe, Bryan decided it was time to buy new loafers.

Here the participle is Noticing.

As with the adverbial phrase, there’s just one exception, and again, you have to zero in on the verb (action) of the main sentence: if the phrase comes directly before the verb (and the sentence is therefore in reverse order), no comma after the participial phrase:

Walking along the boardwalk were throngs of vacationers.

As we noted above, this could be rewritten to turn the sentence around:  Throngs of vacationers were walking along the boardwalk. But you might want to have vacationers at the end in order to emphasize it. 

I hope these few rules will help you always get your sentences off on the right foot! But if you have any questions, please feel free to leave me a comment below—these rules that allow some stylistic leeway can be confusing. A good practice is to complete your first draft without worrying about punctuation rules, then go back and look them up afterwards. And remember to take on just one rule at a time: focus on using it for several days before adding another one into the mix.

I’ll be back next time for our last foray into the complicated world of the comma!