Cannabis, (genus Cannabis), plant belonging to the family Cannabaceae of the nettle order (Urticales). By some classifications, the genus Cannabis comprises a single species, hemp (Cannabis sativa), a stout, aromatic, erect annual herb that originated in Central Asia and is now cultivated worldwide, including in Europe, southern Asia, the Middle East, India, Africa, and the Americas. A tall canelike variety is raised for the production of hemp fibre, while the female plant of a short branchier variety is prized as the more abundant source of the psychoactive substance tetrahydrocannabinol (THC), the active ingredient of marijuana.