text: State variables must be linearly independent; a state variable cannot be a linear combination of other state variables. The minimum number of state variables required to represent a given system, n, is usually equal to the order of the system's defining differential equation. The minimum number of state variables is equal to the order of the transfer function's denominator after it has been reduced to a proper fraction.\n\nIn electronic systems, the number of state variables is the same as the number of energy storage elements in the circuit (capacitors and inductors).