Feedback loop

A process in which an initial change produces effects that reinforce or counteract that change. Reinforcing feedback amplifies change; balancing feedback opposes it.

Causal loop diagram: A diagram showing causal links and feedback loops among variables in a system. Its signed arrows make reinforcing and balancing relationships explicit.
Thermostat: A device that regulates temperature by switching heating or cooling in response to a sensor. It is a familiar negative-feedback controller.
Causal loop: A chain of causal influences that returns to affect an earlier variable. A feedback loop is formed when causal influence closes into a loop.
Feedforward: A control strategy that acts in anticipation of a disturbance rather than correcting measured error. Unlike feedback, it need not wait for an effect to return as input.
Delay (systems theory): A lag between a change in a system and its resulting effect. Delays can make corrective feedback overshoot or oscillate.
Homeostasis: The maintenance of relatively stable internal conditions in an organism. Physiological feedback loops keep variables such as temperature within viable ranges.
System dynamics: An approach to modeling how feedback, delays, and accumulations shape changing systems. It provides a framework for representing loops over time.
Linear system: A system whose outputs obey proportionality and superposition with respect to its inputs. Feedback can create complex behavior even when individual relations are simple.
Oscillation: Repeated variation around a central value or between states over time. Delayed feedback can drive recurring swings instead of steady regulation.
Gene regulatory network: A system of molecular interactions that controls gene expression. Genes and their products can regulate one another through feedback.

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