In cgs, the electric susceptibility is defined as the ratio of polarization P to electric field strength E,

(1)

where is the electric permittivity (Purcell 1985, p. 372).

In MKS, the electric susceptibility is defined as

(2)

where is the permittivity of free space (Griffiths 1998, p. 156)

D, Electric Displacement, Electric Permittivity, Electrical Conductance, Magnetic Susceptibility, Polarization