Definition:Greatest Set by Set Inclusion/Class Theory

Definition
Let $\mathcal A$ be a set of sets or a class of sets.

Then a set $M$ is the greatest element of $\mathcal A$ (with respect to the subset relation) iff:


 * $M \in \mathcal A$ and
 * $\forall S: \left({S \in \mathcal A \implies S \subseteq M}\right)$