- 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
- an area of action, knowledge, etc.
- either lateral half of the cerebrum or cerebellum
ME hemisperie < L hemisphaerium < Gr hēmisphairion: see hemi- & sphere