A proper subset B of a set C, denoted , is a subset that is strictly contained in C and so necessarily excludes at least one member of C.
This means that the number of elements in B must be at least 1 less than the number of elements in C. If the number of elements in C is 8, then the maximum number of elements in B can be 7.
The empty set is a proper subset of any nonempty set. Hence, the minimum number of elements in B can be 0.
