Abstract
This article provides a discussion on implicational hierarchies. It presents the examples of typological hierarchies and considers in turn syntactic, morphosyntactic, and lexical hierarchies. A well-known syntactic hierarchy is the Accessibility Hierarchy. The Agreement Hierarchy and the Animacy Hierarchy are the two well-established examples of morphosyntactic hierarchy. The Berlin and Kay Hierarchy is a famous typological hierarchy for lexis. Any proposed hierarchy must be justified by the range of data that it explains and the closeness of fit between the data and the claim made. The use of hierarchies for research on individual languages is described. The article finally deals with the extension of hierarchies and the relation of hierarchies to semantic maps.