Differentia

Differentia (Plural: Differentiae)

A differentia is a difference between two things. Differentiae are the properties, features, or attributes that distinguish a type from other types that have a common supertype. The term comes from Aristotle's method of defining new types by stating the genus or supertype and stating the differentiae that distinguish the new type from its supertype. This is the most famous approach to definition, by which a word must first be defined according to the class (or genus) of things to which it belongs. Then the word must be distinguished (or differentiated, hence differentia) from the other things within that class.

Aristotle's method of definition is still much used in dictionaries as well as in knowledge bases in artificial intelligence. In recent years this view has been somewhat challenged by points of view related to Wittgenstein's philosophy and related points of view. (See essence in Epistemological Lifeboat).

Literature:

Wikipedia. The free encyclopedia. (2006). Genus-differentia definition. http://en.wikipedia.org/wiki/Definition_by_genus_and_difference