A little extra information.
Today’s topic is appositives.
Guest-writer Bonnie Trenga writes,
Today, we have to decide whether information is essential or extra because if it’s extra, we’ll need some extra commas. The concept I’m referring to is called an appositive. A listener, Mary, raised this topic when she asked, “Is it OK to start a sentence with ‘A vocational counselor, Jane Smith, has agreed to help me get a job’? Is this OK or should it be ‘Vocational counselor, Jane Smith, has agreed to help me get a job’?” Well, Mary, yes in one case but no in another.
What Is an Appositive?
Before we get into the details of this fairly complicated topic, we need to find out what an appositive is. It’s a noun or a noun phrase that is placed next to another noun or noun phrase to help identify it. (1) So at the beginning of this episode, I said, “a listener, Mary, raised this topic.” In this sentence, the subject is “a listener.” The name Mary is an appositive.
Essential or Extra?
Appositives can be essential information or extra information. Only appositives that are extra information get commas. The question now is whether the name Mary is essential or extra. The rule for appositives is that if the information is essential, you don’t use commas. If it is extra, you use extra commas. (2) Remember: extra information, extra commas.
I’m sorry to tell you, Mary, but your name was not essential; that is why it was surrounded with commas. Of course your name is essential to you, but it’s not essential to that sentence. The sentence was about the fact that a listener—one of many—had a question about appositives. You could leave out the appositive and the sentence would still convey the same thought: “A listener raised this topic.”
Now, if this podcast had only one listener, the story would be different. If Mary were the only listener, and we're glad she's not, then the sentence would have to go like this: “Listener Mary asked about appositives.” It would be incorrect to put commas around her name because her name is essential identifying information. You couldn’t delete the appositive in this case because the sentence would not make sense. You couldn’t say, “Listener asked about appositives.”