Definition of "hemisphere"

(astronomy, astrology) Half of the celestial sphere, as divided by either the ecliptic or the celestial equator .

(figuratively) A realm or domain of activity .  quotations  examples

(geography) Half of the Earth, such as the Northern Hemisphere, Southern Hemisphere, Western Hemisphere or Eastern Hemisphere, Land Hemisphere, Water Hemisphere etc.  examples

(geometry) Any half-sphere, formed by a plane intersecting the center of a sphere.  examples

(cartography) A map or projection of a celestial or terrestrial hemisphere .  examples

(anatomy) Either of the two halves of the cerebrum.  examples