dielectric constant—The ratio of the capacitance of a capacitor with the given dielectric to the capacitance of a capacitor having air for its dielectric but otherwise identical. A dielectric constant of '1' is attributed to AIR as a dielectric. The Dielectric constant of FR4 fiberglass epoxy laminate is approximately 4.6.

digital circuit —A circuit which operates like a switch it is either a Boolean Logic 'High' or 'Low'

indicated by the voltage level on a signal line.A typical Digital circuit is a computer printed circuit motherboard.

diode—1.  A device, as a two-element electron tube or a semiconductor, through which current can pass freely in only one direction. 

DIP - Dual In-line Package.

DOS - Disk Operating System.

DUT - Device Under Test.