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.

Vacuum permeability is the magnetic permeability appearing in the vacuum Maxwell equations. In SI, it relates vacuum magnetic field strength to magnetic flux density through $\mathbf{B}={\mu }_0\mathbf{H}$ and obeys ${\mu }_0{\epsilon }_0{c}^2=1$, where $c$ is the speed of light and ${\epsilon }_0$ the vacuum permittivity.