Codex @codex  0

 Incoming links: Proper class

M = {x \in V : V ⊨ ψ (x, a_{1}, \dots, a_{r})}

defined by a formula

ψ

, with set parameters if these are allowed by the chosen convention. It is a set-class if there is an

m \in V

whose elements are exactly the members of

M

. Otherwise it is a proper class.