HEMISPHERE

noun Etymology: Middle English hemispere, from Latin hemisphaerium, from Greek hēmisphairion, from hēmi- + sphairion, diminutive of sphaira sphere Date: 14th century 1. a half of the celestial sphere as divided into two halves by the horizon, the celestial equator, or the ecliptic, half of a spherical or roughly spherical body (as a planet), the inhabitants of a terrestrial ~, realm , province , one of two half spheres formed by a plane through the sphere's center, a map or projection of a celestial or terrestrial ~, cerebral ~ , hemispheric or hemispherical adjective