\begin{definition}[Definition:Entropic Structure]
An '''entropic structure''' is an algebraic structure $\struct {S, \circ}$ such that $\circ$ is an entropic operation.
That is, such that:
:$\forall a, b, c, d \in S: \paren {a \circ b} \circ \paren {c \circ d} = \paren {a \circ c} \circ \paren {b \circ d}$
\end{definition}