The unit of measure used for electrical resistance is the ohm, represented by the Greek letter omega (Ω). Named after the German physicist Georg Simon Ohm, who formulated Ohm's Law, the ohm quantifies how much a material resists the flow of electric current. One ohm is defined as the resistance between two points in a conductor when a voltage of one volt produces a current of one ampere. Understanding resistance is crucial for designing electrical circuits and systems, as it affects power dissipation and the overall efficiency of electrical devices.