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[2DX] Zermelo–Fraenkel set theory with the axiom of choice included is abbreviated ZFC, whereas ZF refers to the axioms of Zermelo–Fraenkel set theory (without the axiom of choice).
[2DX] Zermelo–Fraenkel set theory with the axiom of choice included is abbreviated ZFC, whereas ZF refers to the axioms of Zermelo–Fraenkel set theory (without the axiom of choice).