Genus–differentia definition

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A genus–differentia definition is a type of intensional definition, and it is composed of two parts: a genus (or family): An existing definition that serves as a portion of the new definition; all definitions with the same genus are considered members of that genus. the differentia: The portion of the definition that is not provided by the genus. For example, consider these two definitions: a triangle: A plane figure that has 3 straight bounding sides. a quadrilateral: A plane figure that has 4 straight bounding sides. Those definitions can be expressed as one genus and two differentiae: one genus: the genus for both a triangle and a quadrilateral: "A plane figure" two differentiae: the differentia for a triangle: "that has 3 straight bounding sides." the differentia for a quadrilateral: "that has 4 straight bounding sides." The use of a genus (Greek: genos) and a differentia (Greek: diaphora) in constructing a definition goes back at least as far as Aristotle (384–322 BCE). Furthermore...

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