Example 1: “Reward a student.” No class or year is specified: unrestricted in those respects.
Example 2: “Reward a student in grade ten.” The grade restriction excludes other students.
Example 3: “Buy a piece of cloth.” No colour condition.
Example 4: “Buy white cloth.” White is now required.
The object remains the same across each pair. What changes is the additional qualification that determines which instances satisfy the request.