Subsets

• The set A is a subset of the set B (A ⊆ B) if every element of set A is also an element of set B.
• The set A is a proper subset of the set B (A ⊂ B) if every element of set A is also an element of set B and A ≠ B.
• The empty set is a subset of every set.
• If n(S) = c, then there are 2^c subsets of S.