Genus
A group of closely related species, given as the first word of a scientific name.
A genus gathers species that are close relatives. Its name is the first word of the scientific name and always has a capital letter. All roses belong to the genus Rosa, all tulips to Tulipa, all true lilies to Lilium. The plural is genera. Many genus names have become everyday words: chrysanthemum, dahlia, gladiolus, hibiscus, iris and zinnia are all genus names. When botanists revise a genus, familiar plants can change their names.