\begin{definition}[Definition:Entropic Operation]
Let $\circ$ be an operation on a set $S$ such that:
:$\forall a, b, c, d \in S: \paren {a \circ b} \circ \paren {c \circ d} = \paren {a \circ c} \circ \paren {b \circ d}$
Then $\circ$ is '''entropic'''.
\end{definition}