what is genus in biology

In biology, a genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses. It is a category ranking below family and above species. A genus consists of structurally or phylogenetically related species or a single isolated species exhibiting unusual differentiation. The genus name is the first word of a binomial scientific name, and it is always capitalized. For example, in the scientific name "Panthera leo," Panthera is the genus name. The genus is a fundamental unit in biological classification and is essential in the binomial nomenclature system for naming organisms. It is comprised of species with common attributes, and it may contain one or more species. The classification of species into genera is somewhat arbitrary, and there are no objective criteria for grouping species into genera.