Hierarchy

Originally, hierarchy meant rule by priests. Since hierarchical churches such as the Roman Catholic and Eastern Orthodox churches had tables of organization that were "hierarchical" in the modern sense of the word, that modern sense came about.

In the modern sense of the word, a hierarchy is a tree- or pyramid-like organization of a group of entities. See the illustration for an example. Different fields use the word in slightly different ways, but a particular definition, which the article will attempt first, captures the core of almost all uses.