Sorry for the long absence! I’m finally reasonably settled back into my “day job,” new house, and so forth. It’s about time to dig back into my shadowy secret life of fiction-writing, reviewing, and blogging. I figured I’d kick things off with a post about commas. I mean, really, you can never talk too much about commas, right? So here we go: apposition.

Apposition is the placement of two grammatical elements (words, phrases) side by side in a mutually defining or modifying relationship. Here’s an example:

My father, Frederick Brown, recently moved to Portland and bought a house next door to my sister Alice Smith.

In the above sentence, “my father” is in apposition to “Frederick Brown,” and “my sister” is in apposition to “Alice Smith.”

The $64,000 question is why “Frederick Brown” has commas around it but “Alice Smith” doesn’t. The reason? “Frederick Brown” is a non-restrictive or non-essential appositive — since the speaker only has one father, “my father” and “Frederick Brown” are synonymous. “Frederick Brown” doesn’t restrict the category of “my father,” so it’s non-essential. Non-essential or non-restrictive (these terms are interchangeable) appositives need commas before and after.

In contrast, “my sister” and “Alice Smith” might or might not be synonymous. Why? Because the speaker could have more than one sister. By not putting commas around “Alice Smith,” the speaker is as good as telling you that she has other sisters besides Alice. “Alice Smith” is a restrictive or essential appositive because the category of “my sister” needs to be restricted: which of the speaker’s sisters now has her father as a neighbor? Alice (rather than Susan or Tanya).

Errors in choosing whether or not to comma around appositives are quite common. My students often produce sentences like this one:

Shakespeare’s play, King Lear, is bleakly nihilistic.

Why is that wrong? Because Shakespeare wrote many plays, so “Shakespeare’s play” and “King Lear” are not synonymous. “King Lear” is an essential appositive because the category of “Shakespeare’s play” needs to be restricted. Therefore “King Lear” should not have commas around it.

Now if you said, “Shakespeare’s final romance, The Tempest, is less preoccupied with loss than his earlier forays into that genre,” you’d be fine. Why? Because Shakespeare could only have written one of his romances last. That category can, by definition, only include one play, so “The Tempest” and “Shakespeare’s final romance” are synonymous. “The Tempest” is a non-restrictive or non-essential appositive and therefore needs commas.

Incidentally, the same restrictive/non-restrictive rules apply to commas around clauses:

You should never ride motorcycles, which are dangerous.

You should never ride motorcycles that are dangerous.

In the first sentence above, “which are dangerous” is non-restrictive: the speaker is labeling all motorcycles dangerous and to be avoided. But in the second sentence, “that are dangerous” is restrictive: the speaker is telling you that only a subset of motorcycles (the dangerous ones) should be avoided. It’s nice when writers use “that” to begin restrictive clauses and “which” to begin non-restrictive ones; it makes the distinction more evident. But the which-vs.-that rule isn’t universal, and you will see “which” being used in both cases. That means the comma is the sole true indicator of restrictiveness vs. non-restrictiveness.