Based on the dielectric properties it is possible to determine whether or not a material can be categorized as a simple medium.
Given the equation of polarization density P:
P = ε0 · Xe · E
where:
ε0: electric permittivity of free space
Xe: electric susceptibility
E: electric field
A material can have one or more of the following characteristics.
Linear: if the electric susceptibility is independent of E.
Isotropic: If the polarization has the same direction as E.
Homogenous: If the susceptibility is independent of space coordinates.
A material is a simple medium if all three properties are satisfied.