What term is used to describe a quantity or condition varied by a control system?

The term that accurately describes a quantity or condition that is varied by a control system is known as the controlled variable. In a control system, the controlled variable is the specific parameter or condition that the system aims to regulate or maintain at a desired level.

For example, in a heating system, the temperature within a room would be the controlled variable. The system's objective is to ensure that this temperature remains at the set point, which is the desired temperature.

Other terms like manipulated variable and feedback variable serve different functions within a control system. The manipulated variable refers to the input or action that is adjusted to affect the controlled variable, while the feedback variable is a measurement of the controlled variable used to inform the system of its current state, contributing to the adjustment process. The set point is the target value for the controlled variable, setting the desired outcome for the system to achieve.