Use the monic convention $p_A(t)=\det(tI-A)$ for an $n\times n$ matrix. It is a degree-$n$ polynomial whose roots are eigenvalues. Some texts instead use $\det(A-tI)=(-1)^np_A(t)$; its roots are unchanged. For $A=\operatorname{diag}(2,3)$, $p_A(t)=(t-2)(t-3)$.
Like how this is organised?
Build your own knowledge tree on knowen.md: notes, decisions and tasks in one connected markdown graph, shared with your team and your AI agents.