ˈhemə̇ˌsfi(ə)r, -iə noun
Etymology: alteration (influenced by Middle French emisphere ) of Middle English hemispere, hemisperie, from Latin hemisphaerium, from Greek hēmisphairion, from hēmi- hemi- (I) + sphairion small sphere (diminutive of sphaira sphere, ball)
1.
a. : a half of the celestial sphere divided into two halves by the horizon, the celestial equator, or the ecliptic
b. obsolete : the sky above the horizon or overhead
c. : a projection on a plane surface of half of the celestial sphere
2. : realm , province
a hemisphere of special knowledge
a hemisphere of life heretofore unknown to us
a discovery that was to have important repercussions in the hemispheres of French literary life — Times Literary Supplement
3.
a. : a half of the terrestrial globe especially as divided by the equator
sailed down over the equator into the southern hemisphere
or into halves one of which contains Europe, Asia, and Africa and the other the Americas
sailed from Europe for the western hemisphere
b. : a map or projection of one of these halves
c. : the inhabitants of one of these halves of the earth
America's plans did not seem to interest the eastern hemisphere
4. : either of two half spheres formed by a plane through a sphere's center
5. : cerebral hemisphere