Feedback

thumb|A feedback loop where all outputs of a process are available as causal inputs to that process

stability mechanism which occurs when some function of the output of a system, process, mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances

process that occurs in a feedback loop which magnifies a small disturbance

thumb|Biofeedback device for treating posttraumatic stress disorder

howling caused by a circular path in an audio system

positive and negative feedbacks associated with climate change

Observe–orient–decide–act cycle

type of oscillator

thumb|300px|Schematic representation of a self-oscillation as a positive feedback loop. The oscillator V produces a feedback signal B. The controller at R uses this signal to modulate the external power S that acts on the oscillator. If the power is modulated in phase with the oscillator's velocity, a negative damping is established and the oscillation grows until limited by nonlinearities.

Method in feedback control system theory