In biology, kingdom (Latin: regnum, pl. regna) is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla (in zoology) or divisions in botany. The complete sequence of ranks is life, domain, kingdom, phylum, class, order, family, genus, and species.
The International Code of Zoological Nomenclature (ICZN or ICZN Code) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. The rules principally regulate:
Written nomenclatural rules in zoology were compiled in various countries since the late 1830s, such as Merton's Rules and Strickland's codes going back to 1843. At the first and second International Zoological Congresses (Paris 1889, Moscow 1892) zoologists saw the need to establish commonly accepted international rules for all disciplines and countries to replace conventions and unwritten rules that varied across disciplines, countries, and languages.
Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical nomenclature is Linnaeus' Species Plantarum of 1753. Botanical nomenclature is governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which replaces the International Code of Botanical Nomenclature (ICBN).
Botanical nomenclature has a long history, going back to the period when Latin was the scientific language throughout Europe, and perhaps further back to Theophrastus. A key event was Linnaeus’ adoption of binomial names for plant species in his Species Plantarum (1753). Every plant species is given a name that remains the same no matter what other species were placed in the genus, and this separates taxonomy from nomenclature. These species names of Linnaeus together with names for other ranks (such as family, class, order, variety), can serve to express a great many taxonomic viewpoints.
In biological classification, rank is the level (the relative position) in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class.
Each rank subsumes under it a number of less general categories. The rank of species, and specification of the genus to which the species belongs is basic, which means that it may not be necessary to specify ranks other than these.
Biological classification, or scientific classification in biology, is a method of scientific taxonomy used to group and categorize organisms into groups such as genus or species. These groups are known as taxa (singular: taxon).
Modern biological classification has its root in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the Darwinian principle of common descent. With the introduction of the cladistic method in the late 20th century, phylogenetic taxonomy in which organisms are grouped based purely on inferred evolutionary relatedness, ignoring morphological similarity, has become common in some areas of biology. Molecular phylogenetics, which uses DNA sequences as data, has also driven many recent revisions and is likely to continue doing so. Biological classification belongs to the science of biological systematics.