[hemi.sphere] n [ME hemispere, fr. L hemisphaerium, fr. Gk hemisphairion, fr. hemi- + sphairion, dim. of sphaira sphere] (14c) 1 a: a half of the celestial sphere divided into two halves by the horizon, the celestial equator, or the ecliptic b: half of a spherical or roughly spherical body (as a planet); specif: the northern or southern half of the earth divided by the equator or the eastern or western half divided by a meridian c: the inhabitants of a terrestrial hemisphere
2: realm, province
3: one of two half spheres formed by a plane through the sphere's center
4: a map or projection of a celestial or terrestrial hemisphere
5: cerebral hemisphere -- hemi.spher.ic or hemi.spher.i.cal adj