Number of Elements of a Set

The number of DISTINCT elements contained in a finite set A is denoted by $n(A)$, and is also called the CARDINALITY (or cardinal number) of the set A. For example, if $A=\{5,2,3,4\}$, then $n(A)=4$, since A has exactly four distinct elements. Cardinality only counts distinct elements — if a set were somehow described with a repeated entry, that repeat would not add to the count, consistent with the Roster-method …