A hierarchy/Greek: ἱεραρχία, hierarkhia, 'rule of a high priest', from hierarkhes, 'president of sacred rites' is an arrangement of items - objects, names, values, categories, etc. - that are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an important concept in a wide variety of fields, such as philosophy, architecture, design, mathematics, computer science, organizational theory, systems theory, systematic biology, and the social sciences - especially political philosophy. wiki