A set is any well-defined collection considered as a single, abstract object. By ‘well-defined’ is meant that it is always possible to determine for a given set and a given object whether the object is an element of the set. In formal set theory, the term ‘set’ is not defined, but is a primitive term whose meaning is informed purely by the axioms in which it appears.

Citation Info

  • [MLA] “set.” Platonic Realms Interactive Mathematics Encyclopedia. Platonic Realms, 28 Mar 2013. Web. 28 Mar 2013. <>
  • [APA] set (28 Mar 2013). Retrieved 28 Mar 2013 from the Platonic Realms Interactive Mathematics Encyclopedia:


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