Consists of the following:

  1. A set of elements (for Real Number System, elements are all real numbers)
  2. One or more relations expressing some kind of comparison among elements in the set ()
  3. One or more operations on the set of elements (, exponents, radicals)
  4. A list of basic rules or laws that govern the behavior of the elements under the operations and relations (Axioms)

Examples: Real Number System (), set theory (chapter 3), binary systems (only elements are and ).