Taxonomy (biology) new common (or apomorphic) traits. However, certain phenetic methods, such as neighbor joining, have found their way into cladistics, as a reasonable approximation of phylogeny when more advanced methods (such as Bayesian inference) are too computationally expensive. Modern taxonomy uses database technologies to search and catalogue classifications and their documentation. While there is no commonly used database, there are comprehensive databases such as the "Catalogue of Life", which attempts to list every documented species. The catalogue listed 1.64 million species for all kingdoms as of April 2016, claiming coverage of more than three quarters of the estimated species known to
Taxonomy (general) of parts of a whole. Many taxonomies have a hierarchical structure, but this is not a requirement. Taxonomy uses taxonomic units, known as taxa (singular taxon). Wikipedia categories illustrate a taxonomy and a full taxonomy of Wikipedia categories can be extracted by automatic means. Recently, it has been shown that a manually-constructed taxonomy, such as that of computational lexicons like WordNet, can be used to improve and restructure the Wikipedia category taxonomy. In a broader sense, taxonomy also applies to relationship schemes other than parent-child hierarchies, such as network structures. Taxonomies may then include single children with multi-parents, for example,