A genus is a rank in the biological classification system that groups together species that are closely related and share common characteristics. It is positioned above species and below family in the taxonomic hierarchy. For example, the genus Panthera includes species like the lion (Panthera leo) and the jaguar (Panthera onca)
. In binomial nomenclature, the genus name forms the first part of the scientific name of a species and is always capitalized and italicized, such as Homo in Homo sapiens
. The criteria for defining a genus generally include:
- Monophyly: all members share a common ancestor.
- Reasonable compactness: the genus should not be unnecessarily large.
- Distinctness: members should be distinct in ecology, morphology, or biogeography
A genus can contain multiple species or sometimes only a single species (called monotypic genus), like Ginkgo which contains only one species
. In summary, a genus is a group of closely related species that share evolutionary traits and form a distinct lineage within a family
