John's wife, Nancy, is a nice person.Appositives verses unrestrictive adjective clauses
An unrestricted adjective clause is punctuated just like an appositive; therefore, they can sometimes be confused for one another. But it is easy to tell the difference.
An unrestricted adjective clause has two easily identifiable characteristics:
- It always begins with a relative pronoun (Who, whom, whose, which).
- It describes the noun it follows (rather than renaming it).
Finally, you can test for an appositive by replacing the noun with the appositive. If the sentence still makes sense, it's an appositive, not an unrestricted adjective clause.
John, the musician, can also sing.
Test sentence: The musician can also sing. The sentence retains its meaning. The result is the sentence contains an appositive.
John, who is a musician, can also sing.
Test sentence: Who is a musician can also sing. The sentence makes no sense. The result is the sentence contains an unrestricted relative clause.