| under sinusoidal conditions in a medium where the phasors D and E representing respectively the electric flux density and the electric field strength are linearly related, complex quantity ε r defined by the relation:|
D = ε0ε r E
where ε0 is the electric constant
NOTE 1 – The complex relative permittivity is generally frequency dependent. For an isotropic medium the complex relative permittivity is a scalar; for an anisotropic medium it is a tensor.
NOTE 2 – Generally εr is expressed as ε r = ε' r − jε''r where ε'r is the real relative permittivity and ε''r is the dielectric loss index which represents dielectric losses.