Cayley Table

A Cayley Table is a grid that shows the answers for doing a binary operation on a set of elements.

As an example we could choose the set to be {-1, +1} and the binary operation to be Multiplication.

\begin{bmatrix} \cdot & -1 & +1 \\ -1 & +1 & -1 \\ +1 & -1 & +1\end{bmatrix}