Q. I can’t wrap my brain around this question re appositives. In the following sentence, is the man’s name restrictive or nonrestrictive? Ask Ruth’s childhood friend Tom Jones to help.
A. Unfortunately, it’s ambiguous. A lack of commas is supposed to signal restriction: That is, the meaning of “childhood friend” in your sentence would be restricted to Tom Jones, implying that Ruth had other childhood friends as well. Commas (“Ask Ruth’s childhood friend, Tom Jones, to help”), on the other hand, signal nonrestriction: Tom Jones in that sentence would be Ruth’s only childhood friend, so the meaning of the sentence isn’t restricted by the name Tom Jones, which provides extra information. It’s a pretty good system. But be aware that commas in nonrestrictive constructions are often considered optional, which is fine when the most likely meaning is obvious (as in “my wife Georgia”) but unhelpful in a sentence like yours. In other words, we would need more context to know for sure. For more details, see CMOS 6.31, on spousal and other relationship commas.