  We show a parameter-dependent $3\times 3$ non-Hermitian matrix that exhibits
both degeneracy and coalescence of eigenvalues at an exceptional point
(Hermitian and non-Hermitian degeneracies). This simple non-Hermitian model is
suitable for the discussion of those concepts in an undergraduate or graduate
course on quantum-mechanics. We also study the symmetry group responsible for
the degeneracy.
