Feedback is what occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. Feedback may also refer to: Engineering Audio feedback, the "howl" sometimes heard in microphone or guitar amplification systems Video feedback, the optical equivalent of audio feedback, caused when a camera films the image it is producing Positive feedback, a feedback system that responds to perturbation in the same direction as the perturbation Negative feedback, a method of attenuation to restore equilibrium Negative-feedback amplifier, an amplifier designed to stabilize a system and improve performance Human behaviour Corrective feedback, by a parent or teacher to guide a child's learning process Delayed Auditory Feedback, a method of combating stuttering Employee performance appraisal, particularly methods such as 360-degree feedback Science Biofeedback Climate change feedback, for positive and negative feedbacks associated with climate change Mathematics Feedback arc set, in graph theory, a method of eliminating directed graphs Feedback vertex set, in computational complexity theory, the feedback vertex set problem is a graph-theoretical NP-complete problem Comics Feedback (Marvel Comics), a Marvel Comics superhero Feedback (Dark Horse Comics), the winner of Who Wants to be a Superhero? and a Dark Horse Comics superhero Music "Feedback" (Janet Jackson song), 2008 "Feedback" (Kanye West song), 2016 Feedback, a 1944 album by Les Paul Feedback (Spirit album), 1972 Feedback (EP), a 2004 EP by Rush Feedback (Jurassic 5 album), 2006 "Feedback", a song by Covenant from their 1996 album Sequencer Feedback (Derek Webb album), 2010 Feedback (band), a Bangladeshi rock band Other Feedback, a video podcast produced by G4 Feedback (radio series), a BBC Radio Four programme in the UK Feedback, a character in Ben 10: Omniverse Feedback, a design principle in User interface design Feedback loop (email) Causal loop in the context of time travel or the causal structure of spacetime, that is a sequence of events (actions, information, objects, people)