Vacuum permittivity

Absolute dielectric permittivity of free space

Vacuum permittivity, commonly denoted ε0 (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric constant, or the distributed capacitance of the vacuum. It is an ideal (baseline) physical constant.

From Wikipedia, under CC BY-SA. More on occurri.