An organisation with few things, or one thing, at the top and with several things below each other thing. An inverted tree structure. Examples in computing include a directory hierarchy where each directory may contain files or other directories; a hierarchical network (see hierarchical routing), a class hierarchy in object-oriented programming.

(01 Mar 1994)

1. Any system of persons or things ranked one above the other.

2. In psychology and psychiatry, an organization of habits or concepts in which simpler components are combined to form increasingly complex integrations.

Origin: G. Hierarchia, rule or power of the high priest

(05 Mar 2000)