Explanation:

A process theory is a system of ideas that explains how an entity changes and develops. Process theories are often contrasted with variance theories, that is, systems of ideas that explain the variance in a dependent variable based on one or more independent variables. While process theories focus on how something happens, variance theories focus on why something happens. Examples of process theories include evolution by natural selection, continental drift and the nitrogen cycle.
Process theories come in four common archetypes. Evolutionary process theories explain change in a population through variation, selection and retention—much like biological evolution. In a dialectic process theory, “stability and change are explained by reference to the balance of power between opposing entities”