In electromagnetism, permeability is the measure of magnetization produced in a material in response to an applied magnetic field. Permeability is typically represented by the (italicized) Greek letter μ. It is the ratio of the magnetic induction to the magnetizing field in a material. The term was coined by Lord Kelvin in 1872, and is used alongside its electrostatic equivalent, permittivity, coined by Oliver Heaviside in 1885. The reciprocal of permeability is magnetic reluctivity.