ETYM Greek ierarchia: cf. French hiérarchie.
1. A series of ordered groupings of people or things within a system.
2. The organization of people at different ranks in an administrative body; SYN. power structure, pecking order.
Structure consisting of different levels of authority in, for example, a business organization, one above the other. At the top of the hierarchy of a company, for example, is the chair and at the bottom is the shop-floor worker. Each worker in the hierarchy should have a job description that clearly sets out his or her duties and position within it.

A type of organization that, like a tree, branches into more specific units, each of which is “owned” by the higher-level unit immediately above. Hierarchies are characteristic of several aspects of computing because they provide organizational frameworks that can reflect logical links, or relationships, between separate records, files, or pieces of equipment. For example, hierarchies are used in organizing related files on a disk, related records in a database, and related (interconnected) devices on a network. In applications such as spreadsheets, hierarchies of a sort are used to establish the order of precedence in which arithmetic operations are to be performed by the computer. See also hierarchical file system.