Constitutive relations

Constitutive relations specify how matter responds to fields. A homogeneous isotropic linear electromagnetic medium obeys $\mathbf{D}=\epsilon \mathbf{E}$ and $\mathbf{B}=\mu \mathbf{H}$.

Electromagnetic permeability relates magnetic flux density to magnetic field strength through $\mathbf{B}=\mu \mathbf{H}$ in an isotropic linear medium.