: the study of the general principles of scientific classification :systematics
: orderly classification of plants and animals according to their presumed natural relationships
In biology, the classification of organisms into a hierarchy of groupings, from the general to the particular, that reflect evolutionary and usually morphological relationships: kingdom, phylum, class, order, family, genus, species. The black-capped chickadee, for example, is an animal (kingdom Animalia) with a dorsal nerve cord (phylum Chordata) and feathers (class Aves: birds) that perches (order Passeriformes: perching birds) and is small with a short bill (family Paridae), a song that sounds like chik-a-dee (genus Poecile), and a black-capped head (species atricapillus). Most authorities recognize five kingdoms: monerans (prokaryotes), protists, fungi (seefungus), plants, and animals. Carolus Linnaeus established the scheme of using Latin generic and specific names in the mid-18th century; his work was extensively revised by later biologists.