The composition of a genus is determined by a taxonomist. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful:
Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera.
The term comes from the Latin genus ("origin; type; group; race"), a noun form cognate with gignere ("to bear; to give birth to"). Linnaeus popularized its use in his 1753 Species Plantarum, but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera".
The rules for the scientific names of organisms are laid down in the Nomenclature Codes, which are employed by the speakers of all languages, giving each species a single unique Latinate name. The standard way of scientifically describing species and other lower-ranked taxa is by binomial nomenclature. The generic name forms its first half. For example, the gray wolf's binomial name is Canis lupus, with Canis (Lat. "dog") being the generic name shared by the wolf's close relatives and lupus (Lat. "wolf") being the specific name particular to the wolf. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany. Especially with these longer names, when the generic name is known from context, it is typically shortened to its initial letter. Another example is a Latinized surname, as in the Roborovski hamster's binomen, Phodopus roborovskii, after the species' discoverer, Russian Lt. Vsevolod Roborovsky. Phodopus for the dwarf hamster genus, from Greek for "padded foot", and roborovskii for the common name and discoverer.