Grammar

2.319 apposition

When you want to give further information about someone or something by using a noun group which describes them or identifies them, you can put this noun group after the headword. This is often called apposition. The use of noun groups in apposition is closely associated with defining and non-defining relative clauses which is explained in paragraphs 8.83 to 8.111.

2.320

If you put this noun group after the main noun group, a comma is almost always put after the main noun group because the second noun group is separate from it, not part of it.

...the sifaka, a beautiful creature with pure white fur.
...Orville Wright, the first man to fly.
...Dan Melnick, the head of MGM.
...Steve Race, the musician and broadcaster.
Her mother, a Canadian, died when she was six.
...a book by a distinguished Scotsman, Ramsey Weir.

If you put this noun group before the main noun group, you can choose whether to use a comma separate the two noun groups or not.

...the American writer Alvin Toffler.
...Joan's husband, Jim Inglis.