What is the purpose of derivative action in a PID controller?

Derivative action responds to the rate of change of error, providing anticipatory control. It applies corrective action based on how fast the error is changing, not just its magnitude. Derivative is useful for slow processes where early correction prevents overshoot. However, derivative amplifies noise, so it is often used with filtering or omitted entirely (PI control) for noisy processes. Derivative time (Td) determines the strength of this predictive response.