 The SI unit for permittivity is farad per meter (F/m).The permittivity is often represented by the relative permittivity formula_4 which is the ratio of the absolute permittivity formula_5 and the vacuum permittivity formula_6

This dimensionless quantity is also often and ambiguously referred to as the "permittivity".Another common term encountered for both absolute and relative permittivity is the "dielectric constant" which has been deprecated in physics and engineering as well as in chemistry.