- system structure where output feeds back as input, modifying subsequent behavior
- positive (amplifying) feedback: output reinforces the process, driving exponential growth or collapse
- examples: compound interest, viral spread, ice-albedo effect, bank runs
- negative (stabilizing) feedback: output counteracts the process, maintaining equilibrium
- examples: thermostat, blood sugar regulation, predator-prey dynamics
- ubiquitous in biology, economics, engineering, and climate
- control theory formalizes feedback through transfer functions and stability analysis
- delay in feedback loops causes oscillation and overshoot
- cybernetics (Wiener) placed feedback at the center of self-regulating systems