Genus, plural genera, biological classification ranking between family and species, consisting of structurally or phylogenetically related species or a single isolated species exhibiting unusual differentiation (monotypic genus). The genus name is the first word of a binomial scientific name (the species name is the second word) and is always capitalized.
Biologists have used binomial nomenclature to identify species since it was first employed by Swedish naturalist and explorer Carolus Linnaeus after the publication in Species Plantarum in 1753. (See also taxonomy; phylogenetics.)
Source: Britannica https://www.britannica.com/science/genus-taxon