The root locus method is based on studying the effects of feedback on the open–loop transfer function of a linear system.

The open–loop transfer function is usually expressed in terms of the s–plane, which is a complex plane in which the real and imaginary parts of the s–variable are plotted.

The s–plane is divided into regions, which are referred to as the locus of the poles. As the parameter of the system is varied, the poles of the transfer function move around the s–plane and the locus of the poles is traced out.

Root locus diagrams are used to analyze the stability of a system by determining the locus of the poles.

The stability of a system can be determined by examining the locus of the poles. A system is considered to be stable if all the poles of the system are located in the left half of the s–plane.