Consists of the following:
- A set of elements (for Real Number System, elements are all real numbers)
- One or more relations expressing some kind of comparison among elements in the set ()
- One or more operations on the set of elements (, exponents, radicals)
- 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 ).