/hem"i sfear'/ , n.
1. ( often cap. ) half of the terrestrial globe or celestial sphere, esp. one of the halves into which the earth is divided. Cf. Eastern Hemisphere, Western Hemisphere, Northern Hemisphere, Southern Hemisphere .
2. a map or projection representing one of these halves.
3. a half of a sphere.
4. Anat. either of the lateral halves of the cerebrum or cerebellum.
5. the area within which something occurs or dominates; sphere; realm.
[ 1325-75; hemisphaerium hemisphaírion; r. ME emysperie emispere ]