Class

Subclass

Let be classes. A subclass is a class whose elements are all elements of , #m/def/set i.e.

A proper subclass is is a subset that is not equal to its superset, i.e.

noting the Axiom of Extensionality for Classes. Note these definitions are identical to that of a subset, but with set replaced by class.

#state/tidy | #lang/en | #SemBr