Common Name: 

Some 100-150 species of deciduous, sometime evergreen, shrubs; upright, arching, or climbing, stems usually with prickles ("thorns") or bristles.  Leaves alternate, compound (odd pinnate), occasionally simple, with persistent stipules, leaflets toothed.  Flowers solitary or in clusters at the end of lateral shoots, usually 5 sepals and 5 petals, numerous stamens and pistils.  The pistils are usually enclosed by a urn-shaped receptacle which develops into a orange or red berry-like fruit (hip) when ripe; it contains many achenes.   Native to temperate and subtropical regions in the Northern Hemisphere; in Europe, North America to northern Mexico, Africa to Ethiopia, in Asia to the Himalayas and the Philippines.
Rosa: Latin name for these plants.

The New Royal Horticultural Society Dictionary of Gardening (Huxley, 1992) points out that "problems of classification and naming are rife in this genus" and that "a new revision is urgently needed", the last complete account of Rosa was by Lindley (Rosarum Monographia) in 1820.