Thermostat

A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint... A thermostat operates as a "closed loop" control device (negative feedback), as it seeks to reduce the error between the desired and measured temperatures. Sometimes a thermostat combines both the sensing and control action elements of a controlled system, such as in an automotive thermostat. The word thermostat is derived from the Greek words θερμός thermos, "hot" and στατός statos, "standing, stationary". https://en.wikipedia.org/wiki/Thermostat