noun hemi·sphere \ ˈhe-mə-ˌsfir \
|Updated on: 19 Aug 2018

Definition of hemisphere

1 a : a half of the celestial sphere as divided into two halves by the horizon (see horizon 1b), the celestial equator, or the ecliptic
b : half of a spherical or roughly spherical body (such as a planet); specifically : the northern or southern half of the earth as divided by the equator (see equator 2) or the eastern or western half as divided by a meridian (see meridian 4a(2))
  • affected by the weather in the other hemisphere
c : the inhabitants of a hemisphere of the Earth
2 : an area of knowledge or activity : sphere, province
  • a hemisphere of life heretofore unknown to us
3 : one of two half spheres (see 1sphere 2a) formed by a plane (see 1plane 2a) through the sphere's center : half of a round object
4 : a map or projection of a celestial hemisphere (see hemisphere 1a) or a terrestrial hemisphere (see hemisphere 1b)
5 : cerebral hemisphere
  • an injury to the left hemisphere


play \ˌhe-mə-ˈsfir-ik, -ˈsfer-\ or hemispherical play \ˌhe-mə-ˈsfir-i-kəl, -ˈsfer-\ adjective

Examples of hemisphere in a Sentence

  1. a tumor in the right cerebral hemisphere

Recent Examples of hemisphere from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hemisphere.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Did You Know?

Hemisphere includes the prefix hemi-, meaning "half". The northern and southern hemispheres are divided by the equator, the circle halfway between Earth's two poles. The eastern and western hemispheres aren't divided so exactly, since there are no poles in the Earth's east-west dimension. Often the dividing line is said to be the "prime meridian"—the imaginary north-south line that runs through Greenwich, England, from which all longitude is calculated (itself being the 0° meridian). But for simplicity's sake, the eastern hemisphere is often said to include all of Europe, Africa, Australia, and Asia, while the western hemisphere contains North and South America and a great deal of ocean.

Origin and Etymology of hemisphere

Middle English hemispere, from Latin hemisphaerium, from Greek hēmisphairion, from hēmi- + sphairion, diminutive of sphaira sphere

HEMISPHERE Defined for English Language Learners


Definition of hemisphere for English Language Learners

  • : a half of the Earth

  • : half of a sphere : half of a round object

  • : either of the two halves of the brain

HEMISPHERE Defined for Kids


noun hemi·sphere \ ˈhe-mə-ˌsfir \

Definition of hemisphere for Students

1 : one of the halves of the earth as divided by the equator or by a meridian
2 : a half of a sphere
3 : either the left or the right half of the cerebrum


\ˌhem-ə-ˈsfir-ik, -ˈsfer-\ or hemispherical \-ˈsfir-i-kəl, -ˈsfer-\ adjective

Medical Dictionary


noun hemi·sphere \ -ˌsfi(ə)r \

medical Definition of hemisphere

: half of a spherical structure or organ: as
b : either of the two lobes of the cerebellum of which one projects laterally and posteriorly from each side of the vermis

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resembling the blue of the sky

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