The first rigorous axiomatization of set theory was presented by Ernst Zermelo (1871–1953) in 1908, and its development by A. A. Fraenkel (1891–1965), adding the axiom of replacement, is known as ZF. If the axiom of choice is added it is known as ZFC. For other axioms see choice, extensionality, power set, replacement, sum set.
Philosophy dictionary. Academic. 2011.