Do commas trip you up? You aren’t alone.

Today we’re taking a brief look at when to put commas to work around appositional phrases and when to give commas the day off.

Here’s the Merriam-Webster definition of apposition:

a grammatical construction that consists of two nouns or noun equivalents referring to the same person or thing, standing in the same syntactical relation to the rest of the sentence without being joined to each other by a coordinating conjunction, and typically adjacent to each other (such as the poet and Burns in “a biography of the poet Burns”, my sister and Jane in “this is my sister Jane”, John and a bashful child in “John, a bashful child, was afraid of strangers”, or the fact and that he is rich in “the fact that he is rich is obvious”)

Helpful?

Here’s my more plain-Jane definition:

Appositives and Appositional phrases. Nouns or phrases functioning as nouns that stand next to each other in a sentence and refer to the same person or thing, where the second noun (or noun phrase) narrows or gives more explanatory information about the first.

In the M-W definition, do you see the commas around “a bashful child”? Sometimes we must enclose an appositional phrase or noun with commas; sometimes not. The decision depends on whether the information of the apposition is restrictive or nonrestrictive.

Restrictive. Narrows the identification of the first noun or noun phrase and is essential to the meaning of the sentence. No commas used.

Nonrestrictive. Gives additional information about first noun or noun phrase, but the sentence would have essentially the same meaning without it. Commas should set off the phrase.

Examples

Usually, as in “John, a bashful child,” appositives that follow proper names are nonrestrictive; the proper name adequately identifies the person, place, or thing and the appositive gives more information. But when the name follows a more generic noun, we must pay attention to whether the generic noun sufficiently reduces the pool of candidates it could refer to or whether the appositive is needed (restrictive) to narrow the meaning down for clear identification.

So, in the United States, the name of a spouse following the phrases “my husband” or “my wife” should generally have commas around the name: My husband, John, took me out for our anniversary. The name is nonrestrictive because the generic noun can refer to only one person.

If, however, I said, “My sister Laura is a veterinarian,” would Laura require commas or not? In this case, context is needed. I have two sisters; therefore, the name is restrictive, narrowing down which sister I mean (no commas). If I had only one sister, the situation would be the same as with husband or wife and would require commas around the name. (If the number of siblings is unknown, assume the name is restrictive.)

The same idea of needing context occurs in other situations, too.

Harper Lee’s book To Kill a Mockingbird has remained a classic for more than fifty years.

Several years ago, that sentence would have required commas as Lee had published only one book. Now that another manuscript has been published, we need the name of the title to understand which book the sentence is meaning (restrictive).

Other slight changes to the sentence can also change the need for commas:

Harper Lee’s debut, To Kill a Mockingbird, has remained a classic for more than fifty years.

An author can have only one debut; therefore, the title is nonrestrictive.

Final Note

One last thought to consider when you are placing commas around nonrestrictive appositional phrases—they come in pairs. Probably the most common mistake regarding these commas is to use the first one and forget the second, especially if the appositional phrase is somewhat long.