A plant genus is a classification category in the biological hierarchy that groups together species that share common characteristics. Each genus contains one or more species, which are the basic units of classification. For example, the genus Rosa includes various species of roses, such as Rosa rubiginosa and Rosa gallica. Genus names are always capitalized and italicized in scientific writing. They help scientists and botanists communicate more effectively about plants. The genus is part of a larger classification system that includes family, order, and kingdom, allowing for a structured understanding of plant diversity and relationships.