Pronunciation: (hem'i-sfēr"),[key] —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.