A genus is a taxonomic category ranking used in biological classification that is below family and above species. Species exhibiting similar characteristics comprise a genus.In binomial nomenclature, the genus is used as the first word of a scientific name in which the first letter is capitalized.
The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles, which have about 1180 genera, the most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species.