1. a clear ordering of individuals on some behavioral dimension, such as dominance–submission. A linear hierarchy occurs when all individuals can be arrayed in a strict transitive order along a continuum (see dominance hierarchy; organizational hierarchy). Often, however, a hierarchy is more complex, with some individuals having equal status or acting in coalitions, or with ordering based on different factors (see animal dominance).

2. in neuroscience, an organization of control systems such that one area of the brain controls another, which in turn may control neuromuscular action.