cardinality

from WordNet (r) 3.0 (2006)

cardinality
    n 1: (mathematics) the number of elements in a set or group
         (considered as a property of that grouping)

from The Free On-line Dictionary of Computing (8 July 2008)

cardinality

   <mathematics> The number of elements in a set.  If two sets
   have the same number of elements (i.e. there is a {bijection}
   between them) then they have the same cardinality.  A
   cardinality is thus an {isomorphism class} in the {category}
   of sets.

   {aleph 0} is defined as the cardinality of the first
   {infinite} {ordinal}, {omega} (the number of {natural
   numbers}).

   (1995-03-29)