Electrical Resistance Unit, commonly referred to as OHM (3 letters), is a unit of measurement used to measure the resistance of an electrical circuit. It is represented by the Greek letter Omega (Ω) and is equal to one volt per ampere. The unit is named after German physicist Georg Ohm, who discovered the relationship between voltage, current, and resistance in 1827. OHM is an important unit of measurement in the field of electrical engineering and is used to calculate the power dissipated in a circuit.