Semi Group
A set (\(S\)) with an binary operation (\(\cdot\)) that is associative.
\begin{equation*} \cdot: S \times S \to S \end{equation*}such that:
\begin{equation*} \forall a,b,c \in S, a \cdot (b \cdot c) = (a \cdot b) \cdot c \end{equation*}- An associative Magma.