Abstract. One of the most powerful tools of abstraction used in object-oriented conceptual modelling is the specialisation/generalisation hierarchy, which allows representing taxonomic relationships among classes. A specialisation/generalisation hierarchy (from now on, taxonomy or taxonomic hierarchy) has always two main associated characteristics: the classification and the inheritance concepts. There are, however, different kinds of taxonomic hierarchies (classification, inheritance, role, etc.) which are often confused or misused in modelling. Sometimes, this occurs because one kind of taxonomic hierarchy is used to represent two or more different concepts. In this paper we present a model of useful taxonomic hierarchies for conceptual modelling from an object-oriented perspective. The taxonomic hierarchies that we propose to represent knowledge are based on Aristotle's definition of essence and accident.