An ohm is a unit of measurement used to quantify electrical resistance in a circuit. It is defined as the amount of resistance that allows one ampere of current to flow when one volt of electrical potential is applied. The symbol for ohm is the Greek letter omega (Ω). Ohms are essential in understanding how electrical components interact in a circuit. For example, a resistor is a device specifically designed to provide a certain amount of resistance, measured in ohms, to control the flow of current. This helps ensure that electrical devices operate safely and efficiently.