"Permittivity" is a physical quantity that describes how an electric field affects, and is affected by a dielectric medium, and is determined by the ability of a material to polarize in response to the field, and thereby reduce the total electric field inside the material. Permittivity is often a scalar valued quantity, however in the general case it is tensor-valued.
$\epsilon = \frac{D}{E}$, where $D$ is electric flux density and $E$ is electric field strength.
Applicable units are those of quantitykind:Permittivity
Permittivity