Ordering of phenomena with grades or classes ranked in sequence; central place theory, for example, posits a hierarchy of settlements from regional capitals to hamlets. In a nested hierarchy each level contains/is composed of the level below, with the individuals in that level being smaller-scale sub-systems of the level above. The metasystem (highest level) does not respond to the lowest sub-system directly, as the dynamics of the sub-system are on too small a scale to be of any consequence; in other words, information across any three hierarchical levels is buffered. This suggests that the sensitivity of a system to change takes a different form, depending on where in the hierarchy the drivers of change originate. Whatever your own focus in geography, you will never find hierarchy expressed more clearly than in Couper (2007) TIBG 32, 3. Smith and Kurtz (2003) Geogr. Rev. 93 suggest a hierarchy of coalitions.