An '''open system''' is a [[feedforward]] [[system]] that does not have any [[feedback loop]] to control its output in a [[control system]] in [[systems theory]]. The system is an "open" system because it does not have a feedback loop in its control. In contrast, a [[closed system (control theory)|closed system]] uses on a feedback loop to control the operation of the system. In an open system, the output of this system is not fed back into the input to the system for control or operation. An open system is essentially a feedforward system.
