The term classification can apply to one or all of: the process of classifying (distinguishing and distributing kinds of "things" into different groups) a resulting set of classes (also called "a classification system") the assignment of elements to pre-established classes Classifying – in the broad meaning given above – is a fundamental concept and a part of almost all kinds of activities. Classification itself is an interdisciplinary field of study. Important contributing disciplines include philosophy, biology, knowledge organization, psychology, statistics and mathematics. Definitions Frederick Suppe distinguished two senses of classification: a broad meaning, which he called "conceptual classification" and a narrow meaning, which he called "systematic classification". About conceptual classification Suppe (1989, 292) wrote: "Classification is intrinsic to the use of language, hence to most if not all communication. Whenever we use nominative phrases we are classifying the designated subject as being importantly similar to other entities bearing the same designation; that is, we classify them together. Similarly the use of predicative phrases classifies actions or properties as being of a particular kind. We call this conceptual classification, since it refers to the classification involved in conceptualizing our experiences and surroundings" About systematic classification Suppe (1989, 292) wrote: "A second, narrower sense of classification is the systematic classification involved in the design and utilization of taxonomic schemes such as the biological classification of animals and plants by genus and species. Basic units Hull (1998) suggested "The fundamental elements of any classification are its theoretical commitments, basic units and the criteria for ordering these basic units into a classification". The basic units in a classification system are classes. There is a widespread opinion in knowledge organization and related fields that such classes corresponds to concepts. We can, for example, classify ‘waterfowls’ into the classes “ducks”, “geese”, and “swans”; we can also say, however, that the concept “waterfowl” is a generic broader term in relation to the concepts “ducks”, “geese”, and “swans”. This example demonstrates the close relationship between classification theory and concept theory. A main opponent of concepts as units is Barry Smith (cf. Smith 2004). Arp, Smith and Spear (2015, 5ff) discuss ontologies and criticize the conceptualist understanding. The book writes (7): “The code assigned to France, for example, is ISO 3166 – 2:FR and the code is assigned to France itself — to the country that is otherwise referred to as Frankreich or Ranska. It is not assigned to