The unit used to measure electrical resistance is the ohm, symbolized by the Greek letter omega (Ω). Resistance quantifies how strongly a material opposes the flow of electric current. Introduced by Georg Simon Ohm in the 1820s, the ohm is defined as the resistance between two points when a potential difference of one volt results in a current of one ampere. Understanding resistance is essential in electrical engineering and physics, as it affects circuit performance and efficiency. Various components, including resistors, exhibit defined resistance values, important for designing circuits in electronics and electrical systems.