hemisphere

noun

• a half of a sphere.
• a half of the earth, usually as divided into northern and southern halves by the equator, or into western and eastern halves by an imaginary line passing through the poles.
• a half of the celestial sphere.
• (also cerebral hemisphere) each of the two parts of the cerebrum (left and right) in the brain of a vertebrate: the left hemisphere plays a dominant role in the comprehension of language