From Encyclopediaofmath A square complex matrix $A$ that commutes with its adjoint matrix $A^*$: that is, $AA^*=A^*A$.
See also Normal operator.
The eigenvectors of a normal matrix form an orthonormal system. A matrix $A$ is normal if and only if it is unitarily similar to a diagonal matrix: $\Delta = U^{-1} A U$ with $u$ a unitary matrix.
Categories: [Special matrices]