Context:
When calculating eigenvalues of a real valued matrix $A$ one often constructs an auxiliary polynomial matrix $M(s):= (sI - A)$ and then calculates its determinant $d(s):=\det\Big(M(s)\Big)$ – which is usually called the characteristic polynomial of $A$. The eigenvalues of $A$ are then the roots of that polynomial.
Question:
What is an established (or at least meaningful and self-explanatory) name for the polynomial matrix $M(s)$ (implicitly depending on $A$)?