hemisphere

• hemisphære (archaic)

From Latin hemisphaerium, from Ancient Greek ἡμισφαίριον (hēmisphaírion), from ἡμι- (hēmi-, “half”) + σφαῖρα (sphaîra, “sphere”). Equivalent to hemi- +‎ sphere. Displaced native Old English healftrendel (literally “half-sphere”).

• (Received Pronunciation) IPA^(key): /ˈhɛmɪsfɪə/
• (US) enPR: hĕ'mĭsfîr, IPA^(key): /ˈhɛmɪsfɪəɹ/

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hemisphere (plural hemispheres)

1. (astronomy, astrology) Half of the celestial sphere, as divided by either the ecliptic or the celestial equator [from 14th c.].
2. (figuratively) A realm or domain of activity [1503].
   • 1831, L[etitia] E[lizabeth] L[andon], Romance and Reality. […], volume III, London: Henry Colburn and Richard Bentley, […], →OCLC, pages 91–92:

     Love is the Columbus of our moral world, and opens, at some period or other, a new hemisphere to our view.

3. (geography) Half of the Earth, such as the Northern Hemisphere, Southern Hemisphere, Western Hemisphere or Eastern Hemisphere, Land Hemisphere, Water Hemisphere etc. [1550s].
4. (geometry) Any half-sphere, formed by a plane intersecting the center of a sphere. [1580s].
5. (cartography) A map or projection of a celestial or terrestrial hemisphere [1706].
6. (anatomy) Either of the two halves of the cerebrum. [1804].

• (astronomy: half of the celestial sphere): celestial hemisphere
• (geography: half of the terrestrial sphere): terrestrial hemisphere
• (figuratively: a domain of thought or action): sphere
• (geometry: half of a sphere): half-sphere, half sphere
• (anatomy: either of the two lobes of the cerebellum): cerebral hemisphere
• (cartography: a map showing a projection of a hemisphere): planisphere

• dome