Webster's Revised Unabridged Dictionary · 1913

Hierarchy

Hierarchy (hī"ẽr*ark`y) , noun

[Greek 'ierarchi`a: compare French hiérarchie.]

1.
Dominion or authority in sacred things.
2.
A body of officials disposed organically in ranks and orders each subordinate to the one above it; a body of ecclesiastical rulers.
3.
A form of government administered in the church by patriarchs, metropolitans, archbishops, bishops, and, in an inferior degree, by priests. — Shipley
4.
A rank or order of holy beings.
Standards and gonfalons... for distinction serve Of hierarchies, of orders, and degrees. — Milton

Classification schemes, as in biology, usually form hierarchies.

5.
(Mathematics, Logic, Computers) Any group of objects ranked so that every one but the topmost is subordinate to a specified one above it; also, the entire set of ordering relations between such objects. The ordering relation between each object and the one above is called a hierarchical relation.