What is the meaning of Hemisphere?

Half of the celestial sphere, as divided by either the ecliptic or the celestial equator .

A realm or domain of activity .

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

Any half-sphere, formed by a plane intersecting the center of a sphere. .

A map or projection of a celestial or terrestrial hemisphere .

Either of the two halves of the cerebrum. .

Source: wiktionary.org