1. (magnetic susceptibility) Symbol χm. The dimensionless quantity describing the contribution made by a substance when subjected to a magnetic field to the total magnetic flux density present. It is equal to μr − 1, where μr is the relative permeability of the material. Diamagnetic materials have a low negative susceptibility, paramagnetic materials have a low positive susceptibility, and ferromagnetic materials have a high positive value.
2. (electric susceptibility) Symbol χe. The dimensionless quantity referring to a dielectric equal to P/ε0E, where P is the electric polarization, E is the electric intensity producing it, and ε0 is the electric constant. The electric susceptibility is also equal to εr − 1, where εr is the relative permittivity of the dielectric.