Taxonomy - en.wikipedia.org
Taxonomy (from Ancient Greek: τάξις taxis ”arrangement” and Ancient Greek: νομία nomia ”method”[1]) is the practice and science of classification or the result of it. Taxonomy uses taxonomic units, known astaxa (singular taxon). A resulting taxonomy, a taxonomy, or taxonomic scheme, is a particular classification (“the taxonomy of …”), arranged in a hierarchical structure or classification scheme. Typically this is organized by supertype-subtype relationships, also called generalization-specialization relationships, or less formally, parent-child relationships, typically indicated by the phrase ‘is a kind of’ or ‘is a subtype of’. In such an inheritance relationship, the subtype by definition has the same properties, behaviors, and constraints as the supertype plus one or more additional properties, behaviors, or constraints. For example: car is a kind of vehicle, so any car is also a vehicle, but not every vehicle is a car. Therefore a subtype needs to satisfy more constraints than its supertype. Thus to be a car is more constraint than to be a vehicle. If other kinds of relationships between concepts are also included, a taxonomy is extended into an ontology. Thus various ontologies also include a taxonomy. This holds especially for the upper level ontologies (arrangements of generic concepts).
