The dielectric constant (permittivity) is the amount of electrical energy stored in an insulator when an electrical field is imposed across it.  The dielectric constant is expressed in terms of a ratio to that in a vacuum or (1.000000).  All other factors being equal, greater permittivity of the dielectric gives greater capacitance; less permittivity of the dielectric gives less capacitance.

The following table lists the dielectric constants of various common materials: