ABSTRACT
The notion of a set has always eluded formal definition and, therefore, is taken to be a primitive notion in axiomatic set theory. However, in practice, one can easily work with sets without a formal definition because of their frequent occurrence in various branches of the mathematical sciences. It suffices, therefore, to say that the term “set” refers to a collection of objects. In actual mathematical usage the loose description becomes tighter once the context of the set and the category of objects in it are clear. For instance, all real numbers form a set. The cardinality of a set is a measure of the size of that set. In the case of sets with finitely many elements in them, the cardinality of a set is the same as the number of elements in that set.
