Trac #21992.11: Explain p^s-minimal polynomial

src/sage/matrix/matrix_integer_dense.pyx

@@ -5597,6 +5597,11 @@ cdef class Matrix_integer_dense(Matrix_dense):   # dense or sparse
         integers, the values are the associated `(p^s)`-minimal polynomials
         `\nu_s`, `s\in\mathcal{S}`.
 
+        For `s\ge 0`, a `(p^s)`-minimal polynomial of
+        a matrix `B` is a monic polynomial `f\in \mathbb{Z}[X]` of
+        minimal degree such that all entries of `f(B)` are divisible
+        by `p^s`.
+
         For `0<t\le \max\mathcal{S}`, a `(p^t)`-minimal polynomial is given by
         `\nu_s` where `s=\min\{ r\in\mathcal{S}\mid r\ge t\}`.  For
         `t>\max\mathcal{S}`, the minimal polynomial of this matrix is also a