Two noun phrases are in apposition when one comes after the other and both refer to the same thing.
- Everyone visits the White House, the home of the President.
- Joseph Conrad, the famous English novelist, couldn’t speak English until he was 47.
When the second phrase adds extra information, we use a comma.
When the second phrase identifies the first one, we do not use a comma.
- The novelist Joseph Conrad couldn’t speak English until he was 4 7.
- Pretty 25-year-old secretary Linda Pilkington has shocked her friends and neighbours.
The sentence about Linda is typical of newspaper style.
We can also use apposition to add emphasis. This happens in speech, too.
- The man is a fool, a complete idiot.
Other kinds of phrases can be in apposition.
- The place is miles away, much too far to walk.
- The experts say the painting is quite valuable, worth a lot of money.