See hemisphere in Webster's New World College Dictionary
noun
half of a sphere, globe, or celestial body; specif.,
any of the halves into which the celestial sphere is divided by either the celestial equator or the ecliptic
any of the halves of the earth: the earth is divided by the equator into the N and S hemispheres and by a meridian into the E Hemisphere (containing Europe, Asia, Africa, and Australia) and the W Hemisphere (containing the Americas and Oceania)
a model or map of any of these halves
the countries and peoples of any of the earth's hemispheres