Non-empty part of a set E, that is different from E.
Examples
Consider the set E = {a, b, c, d, e}
- Set A = {a, b} is a proper part of E.
- The empty set Ø = { } is not a proper part of E.
- Set E is not a proper part of E.
Consider the set E = {a, b, c, d, e}