Hierarchy
A hierarchy (from Ancient Greek ἱεραρχία (hierarkhía) 'rule of a high priest', from ἱεράρχης (hierárkhēs) '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 architecture, philosophy, design, church, mathematics, computer science, organizational theory, systems theory, systematic biology, and the social sciences (especially political science).