Hemisphere

noun

1. Half of the celestial sphere, as divided by either the ecliptic or the celestial equator .
2. A realm or domain of activity .
3. Half of the Earth, such as the Northern Hemisphere, Southern Hemisphere, Western Hemisphere or Eastern Hemisphere, Land Hemisphere, Water Hemisphere etc. .
4. Any half-sphere, formed by a plane intersecting the center of a sphere. .
5. A map or projection of a celestial or terrestrial hemisphere .