section_path: Cardinality
section_name: Cardinality
paragraph_text: Cardinality
  
  The cardinality of a set S, denoted | S |, is the number of members of S. For example, if B = {blue, white, red}, then | B | = 3. Repeated members in roster notation are not counted, so | {blue, white, red, blue, white} | = 3, too.
  
  More formally, two sets share the same cardinality if there exists a bijection between them.
  
  The cardinality of the empty set is zero.