Relation between polarization and electric field

In classical electromagnetism, polarization density (or electric polarization, or simply polarization) is the vector field that expresses the density of permanent or induced electric dipole moments in a dielectric material. In a dielectric material the presence of an electric field E causes the bound charges in the material (atomic nuclei and their electrons) to slightly separate, inducing a local electric dipole moment. 
The electric displacement field is a vector field that accounts for the effects of free and bound charge within materials.The electric displacement field is related to the electric field and the polarization density.