Definition:Von Neumann-Bernays-Gödel Set Theory

Definition
Von Neumann-Bernays-Gödel set theory is a system of axiomatic set theory.

Its main feature is that it classifies collections of objects into:


 * sets, whose construction is strictly controlled

and:
 * classes, which have fewer restrictions on how they may be generated.

All sets are classes, but not all classes are sets.

Also known as
Von Neumann-Bernays-Gödel set theory is usually seen abbreviated either as NBG or VNB.