Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identifying spam emails and deciding whether to give someone a driving license.
As well as 'category', synonyms or near-synonyms for 'class' include 'type', 'species', 'forms', 'order', 'concept', 'taxon', 'group', 'identification' and 'division'.
A combat sport, or fighting sport, is a contact sport that usually involves one-on-one combat. In many combat sports, a contestant wins by scoring more points than the opponent, submitting the opponent with a hold, disabling the opponent (knockout, KO), or attacking the opponent in a specific or designated technique. Combat sports share a long history with the martial arts.
Some combat sports (and their national origin) include boxing (Greek-British), Brazilian jiu-jitsu (Japanese-Brazilian), catch wrestling (British-American), jujutsu (Japanese), judo (Japanese), freestyle wrestling (British-American), Greco-Roman wrestling (French), karate (Chinese-Okinawan-Japanese), kickboxing (numerous origins, mainly Southeast Asian), Lethwei (Burmese), mixed martial arts (numerous origins), Muay Thai (Thai), sambo (Soviet/Russian), sanda (Chinese), savate (French), taekwondo (Korean), Vale Tudo (Brazilian), pankration (Ancient Greek), luta livre (Brazilian), and folk wrestling (various).
Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation of things to the classes (classification).
Originally, taxonomy referred only to the classification of organisms on the basis of shared characteristics. Today it also has a more general sense. It may refer to the classification of things or concepts, as well as to the principles underlying such work. Thus a taxonomy can be used to organize species, documents, videos or anything else.
The category of newly industrialized country (NIC), newly industrialized economy (NIE) or middle-income country is a socioeconomic classification applied to several countries around the world by political scientists and economists. They represent a subset of developing countries whose economic growth is much higher than that of other developing countries; and where the social consequences of industrialization, such as urbanization, are reorganizing society.
Information science (sometimes abbreviated as infosci) is an academic field which is primarily concerned with analysis, collection, classification, manipulation, storage, retrieval, movement, dissemination, and protection of information. Practitioners within and outside the field study the application and the usage of knowledge in organizations in addition to the interaction between people, organizations, and any existing information systems with the aim of creating, replacing, improving, or understanding the information systems.
In information science and ontology, a classification scheme is an arrangement of classes or groups of classes. The activity of developing the schemes bears similarity to taxonomy, but with perhaps a more theoretical bent, as a single classification scheme can be applied over a wide semantic spectrum while taxonomies tend to be devoted to a single topic.
In the abstract, the resulting structures are a crucial aspect of metadata, often represented as a hierarchical structure and accompanied by descriptive information of the classes or groups. Such a classification scheme is intended to be used for the classification of individual objects into the classes or groups, and the classes or groups are based on characteristics which the objects (members) have in common.
The sport of sailing involves a variety of competitive sailing formats that are sanctioned through various sailing federations and yacht clubs. Racing disciplines include matches within a fleet of sailing craft, between a pair thereof or among teams. Additionally, there are specialized competitions that include setting speed records. Racing formats include both closed courses and point-to-point contests; they may be in sheltered waters, along coasts, or on the open ocean. Most competitions are held within defined classes or ratings that either entail one type of sailing craft to ensure a contest primarily of skill or rating the sailing craft to create classifications or handicaps.
On the water, a sailing competition among multiple vessels is called a regatta. A regatta consists of multiple individual races. The boat crew that performs best over the series of races is the overall winner. There is a broad variety of races and of sailboats used for racing, from large yacht to dinghy racing. Much racing is done around buoys or similar marks in protected waters, while some longer offshore races cross open water. Boats used for racing include small dinghies, catamarans, boats designed primarily for cruising, and purpose-built raceboats. The Racing Rules of Sailing govern the conduct of yacht racing, windsurfing, kitesurfing, model boat racing, dinghy racing, and virtually any other form of racing around a course with more than one vessel while powered by the wind.
When classification is performed by a computer, statistical methods are normally used to develop the algorithm.
Often, the individual observations are analyzed into a set of quantifiable properties, known variously as explanatory variables or features. These properties may variously be categorical (e.g. "A", "B", "AB" or "O", for blood type), ordinal (e.g. "large", "medium" or "small"), integer-valued (e.g. the number of occurrences of a particular word in an email) or real-valued (e.g. a measurement of blood pressure). Other classifiers work by comparing observations to previous observations by means of a similarity or distance function.
Hierarchical classification is a system of grouping things according to a hierarchy.
In the field of machine learning, hierarchical classification is sometimes referred to as instance space decomposition, which splits a complete multi-class problem into a set of smaller classification problems.