I’m a big fan of Kurt Vonnegut, Jr. Not only did he write compelling, satirical stories but also he wrote simple, straightforward sentences. As I was re-reading Breakfast of Champions (for the 5th or 6th time) this weekend, I came across this great sentence.
He saw a bathtub toy, a little rubber duck, lying on its side on the grating over a storm sewer.
The phrase a little rubber duck is separated from the rest of the sentence with commas, one before and one after. Why?
In this sentence, a little rubber duck is another way of saying a bathtub toy. They mean the same thing, a perfect one-to-one match. It doesn’t tell us which toy is being described. This means a little rubber duck is a non-restrictive appositive.
Rather than adding new content to the sentence, a non-restrictive appositive provides another name for something just written: in this case a bathtub toy. We can remove that phrase and still understand the main point of the sentence. It is unnecessary to understanding what is happening, so we can separate it from the main sentence with commas.
This sentence follows Zen Comma Rule J: Separate non-restrictive appositives with commas.
Need help with commas? Get Zen Comma, a guide to the 17 major uses and misuses of commas. Read more about Zen Comma.