| 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 to entry: The complex relative permittivity is generally frequency dependent. For an isotropic medium, the complex relative permittivity is a scalar quantity; for an anisotropic medium, it is a tensor quantity.
Note 2 to entry: 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.