\begin{definition}[Definition:Class/Zermelo-Fraenkel/Class Variables]
In deriving general results about $\textrm{ZF}$ which mention '''classes''', it is often convenient to have '''class variables''', which denote an arbitrary '''class'''.
By convention, these variables are taken on {{ProofWiki}} to be the (start of) the capital Latin alphabet, i.e. $A, B, C$, and so on.
Category:Definitions/Zermelo-Fraenkel Class Theory
\end{definition}