[[Class]]
# Proper class

A **proper class** is a [[Class]] which is not the element of any other class, and therefore not a [[set]].
If **elementhood** is defined by
$$
\begin{align*}
\ehood(x) \stackrel{\text{def}}\iff (\exists \chood y)[x \in y]
\end{align*}
$$
then a proper class $A$ satisfies $\pchood(A)$.

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