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 ref="module.php?name=Lexikon&file=search&eid=1&query=network">network (see {hierarchical routing}), a {class hierarchy} in {object-oriented programming}. (1994-10-11)