Reactance is a form of opposition that electronic components exhibit to the passage of alternating current (AC) because of capacitance or inductance. When alternating current passes through a component that contains reactance, energy is alternately stored in, and released from, a magnetic field or an electric field. In the case of a magnetic field, the reactance is inductive. In the case of an electric field, the reactance is capacitive. Resistance and reactance combine to form impedance.