The Greek letter () represents the permittivity of open space, absolute permittivity, as well as electric constants, which is symbolized by Epsilon Naught. This same quantity of Epsilon Naught is constant throughout the cosmos.
Permittivity seems to be a measure of its resistance to the production of an electric field.
Its definite defined value in SI unit is .
Its definite defined value in CGS units is and it is unitiless.