Suppose four books are available:
1. An Arabic grammar book.
2. An Urdu grammar book.
3. An Arabic history book.
4. An English dictionary.
“Bring a book” may be satisfied by any suitable book.
“Bring an Arabic book” permits the first or third.
“Bring an Arabic grammar book” is satisfied by the first.
Each relevant added condition narrows eligible instances while leaving the basic class, “book,” intact.