hierarchy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A group of persons or things organized into successive ranks or grades with each level subordinate to the one above.
• noun Categorization or arrangement of a group of people or things into such ranks or grades.
• noun A body of persons having authority.
• noun A group of animals in which certain members or subgroups dominate or submit to others.
• noun One of three main divisions of angels in traditional Christian angelology.

from The Century Dictionary.

• noun The power or dominion of a hierarch; hallowed or consecrated authority in what concerns religious order or government.
• noun Government by ecclesiastical rulers; an ecclesiastical or priestly form of government. —
• noun An order of holy beings regarded as employed in divine government.
• noun A body of persons organized in ranks and orders for the exercise of rule oversacred things; hence, an organized body of ecclesiastics intrusted with government of either church or state; also, a similarly organized body of officials in other systems of government: as, the Roman Catholic hierarchy.
• noun In science, a series of successive terms of different rank. The terms kingdom, order, suborder, family, genus, and species constitute a hierarchy in zoölogy.

from the GNU version of the Collaborative International Dictionary of English.

• noun Dominion or authority in sacred things.
• noun A body of officials disposed organically in ranks and orders each subordinate to the one above it; a body of ecclesiastical rulers.
• noun A form of government administered in the church by patriarchs, metropolitans, archbishops, bishops, and, in an inferior degree, by priests.
• noun A rank or order of holy beings.
• noun (Math., 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A body of authoritative officials organized in nested ranks.
• noun Any group of objects ranked so that every one but the topmost is subordinate to a specified one above it.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a series of ordered groupings of people or things within a system
• noun the organization of people at different ranks in an administrative body