order parameter

An order parameter is a measurable quantity that describes how organized or aligned a system is during a phase transition, like from a liquid to a solid. For example, in magnetism, it could be the overall magnetic alignment of atoms; when aligned, the order parameter is high, indicating a magnetized state. When disorganized, like in a non-magnetic state, it’s low or zero. It helps scientists understand and quantify the change in the system’s structure or behavior as it undergoes a transition, serving as an indicator of the degree of order present.