Electric polarization ($\mathbf{P}$)

Electric polarization is electric dipole moment per unit volume. It produces bound volume and surface chargeAcross an interface, the net bound sheet charge is $({\mathbf{P}}_1-{\mathbf{P}}_2)\cdot \mathbf{n}$, where $\mathbf{n}$ points from medium one to medium two.

The electric displacement is $\mathbf{D}={ϵ}_0\mathbf{E}+\mathbf{P}$ and obeys $\nabla \cdot \mathbf{D}={\rho }_{\mathrm{free}}$. In a linear isotropic dielectric, $\mathbf{D}=ϵ\mathbf{E}$.