1. A periodic variation of an electrical quantity, such as current or voltage.

2. A phenomenon that occurs in an electrical circuit if the values of self-inductance and capacitance in the circuit are such that an oscillating current results from a disturbance of the electrical equilibrium of the circuit.

A circuit that produces oscillations freely is termed an oscillatory circuit. Oscillations that result from the application of a direct-voltage input to the circuit and continue until the direct voltage is removed are termed self-sustaining oscillations. Oscillations that tend to decrease in amplitude with respect to time are known as stable oscillations; unstable oscillations tend to increase in amplitude with respect to time and soon exceed the rated operating conditions of the circuit. See also free oscillations; forced oscillations; damped; parasitic oscillations.