Wikipedia
Diairesis (, "division") is a form of classification used in ancient (especially Platonic) logic that serves to systematize concepts and come to definitions. When defining a concept using diairesis, one starts with a broad concept, then divides this into (at least) two more specific sub-concepts, and this procedure is repeated until a definition of the desired concept is reached. Apart from this definition, the procedure also results in a taxonomy of other concepts, ordered according to a general–specific relation.
The founder of diairesis as a method was Plato. Later ancient logicians (including Aristotle) and practitioners of other ancient sciences have employed diairetic modes of classification, e.g., to classify plants in ancient biology. Although classification is still an important part of science, diairesis has been abandoned and is now of historical interest only.