noun Half of the celestial sphere, as divided by either the ecliptic or the celestial equator .mw-parser-output .defdate{font-size:smaller}.
noun A realm or domain of activity .
noun Half of the Earth, such as the Northern Hemisphere, Southern Hemisphere, Western Hemisphere or Eastern Hemisphere, Land Hemisphere, Water Hemisphere etc. .
noun Any half-sphere, formed by a plane intersecting the center of a sphere. .
noun A map or projection of a celestial or terrestrial hemisphere .