I’m writing this blog for those of you who worry about punctuation as much as I do—which, admittedly, may be a small group. But if you’re a proud member of that grammar-loving club, then this one’s for you.

A few days ago, I discovered I’ve been misusing commas around names for years. (Yes, years.) Naturally, I then scrutinized the first two sentences of this post for correct comma usage—and I think I got them right. But let’s not linger there. Instead, let’s dive into one of the most elusive comma rules: how to handle names that are nonrestrictive, or what grammarians call nonessential information.

Here’s the gist:

When a name appears in a sentence, whether or not you surround it with commas depends on how essential that name is to identifying the person. For example:

My brother, John, was a great pianist.

This sentence implies that I have only one brother. Since “John” isn’t necessary to know who I’m talking about (he’s my one and only brother), his name is considered nonessential—extra information—and should be set off with commas. You could remove “John” and the sentence still makes sense:

My brother was a great pianist.

But what if I have more than one brother?

My brother John was a great pianist.

In this version, “John” is essential because it tells the reader which brother I mean. There’s no comma because the name provides necessary information. Without it, we wouldn’t know who I’m talking about.

I admit this feels counterintuitive. You might assume that using commas emphasizes the name, making it feel more important. But grammatically speaking, commas actually signal that the name is less essential to the core meaning of the sentence.

So, how do you know when to use commas?

Ask yourself:

1. Is this the person’s one and only role or relationship in this context? (Only brother? Only older sister?)
2. Can I remove the name without losing the sentence’s essential meaning?

If the answer to both is yes, then you use commas. If not, skip them.

Let’s look at two examples:

• Jan’s older sister Mary Ellen was going to the store.
  (No commas = Jan has more than one older sister. The name is essential to distinguish which sister.)
• Jan’s older sister, Mary Ellen, was going to the store.
  (With commas = Jan has only one older sister. Her name is additional info—not necessary to understand the sentence.)

Once you get the hang of it, the rule is straightforward. Still, I can see why it trips people up—it definitely did me.

If you’d like to explore this further, here’s the site I found helpful:

Setting off nonrestrictive or nonessential information

Here are a couple of examples from that page:

• I will give the document to my brother, Tom.
  (Only one brother—name is nonessential.)
• I will give the document to my brother Tom.
  (More than one brother—name is essential.)
• Nathaniel Hawthorne’s novel The Scarlet Letter has been made into several movies.
  (Hawthorne wrote multiple novels—title is essential.)
• Nathaniel Hawthorne’s first novel, Fanshawe, was published anonymously in 1828.
  (He had only one first novel—title is nonessential.)

So there you have it: a small but mighty punctuation rule that I now understand and won’t be misusing again—fingers crossed.

Happy comma-ing, friends.

—Len