'Dielectric constant' is an archaic term for relative permittivity. They are one and the same.

The absolute permittivity of a medium is its relative permittivity multiplied by the vacuum permittivity.

The absolute permittivity is a proportionality constant between the electric and displacement field with units of Farad/meters (in SI units). This number is usually very small (e.g. for air: 0.000 000 000 008 85 F/m).

The relative permittivity is a unit-less number scaled upward to present nicer numbers (e.g. for air: 1.0005).

To get the absolute permittivity from the relative permittivity one should multiply with the vacuum permittivity: 8.85418781... E-12 F/m.

14.6

* Wood dry 1.4-2.9 Retrieved from "http://wiki.4hv.org/index.php/Permittivity"