hemisphere

noun

hemi·​sphere ˈhe-mə-ˌsfir 

plural hemispheres

1

a

: a half of the celestial sphere as divided into two halves by the horizon (see horizon sense 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 sense 2) or the eastern or western half as divided by a meridian (see meridian sense 1a(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 sphere entry 1 sense 2a) formed by a plane (see plane entry 1 sense 2a) through the sphere's center : half of a round object

4

: a map or projection of a celestial hemisphere (see hemisphere sense 1a) or a terrestrial hemisphere (see hemisphere sense 1b)

5

: cerebral hemisphere

an injury to the left hemisphere

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.

Examples of hemisphere in a Sentence

a tumor in the right cerebral hemisphere

Recent Examples on the Web

This last characteristic means the aerosols can get spread across the tropics of both hemisphere thanks to the wind patterns around the equator. —Erik Klemetti, Discover Magazine, 18 Apr. 2024

Lunar eclipses are visible for most of the entire hemisphere that’s facing the moon at the time. —Reece Rogers, WIRED, 7 Apr. 2024

The bowl’s hemisphere can summon to mind the 18th-century French architect Étienne-Louis Boullée’s famous unbuilt monument to Newton, a textbook example of Enlightenment idealism. —Michael Kimmelman Clement Pascal, New York Times, 3 Apr. 2024

In most people, the two halves, or hemispheres, of the brain have slightly different anatomies and are dominant for different functions. —Fox News, 2 Apr. 2024

Furthermore, each of our hands is controlled by the opposite brain hemisphere. —Ayelet Waldman, The New Yorker, 30 Mar. 2024

The parts of quilting that require intense focus, like cutting and matching seams, are controlled by something known as the central executive network, which is distributed in both hemispheres. —Ayelet Waldman, The New Yorker, 30 Mar. 2024

And as material moves around the sun, these leftovers typically migrate toward the pole of that hemisphere, which usually cancels out a little of the existing magnetic field there. —Meghan Bartels, Scientific American, 20 Oct. 2023

With five days until the hemisphere’s big election, Sweetmint must dodge a relentless law officer who’s determined to maintain order and an ambitious politician with sights set on becoming the next Chief Executive by any means necessary. —Sarah Yang, Sunset Magazine, 7 Feb. 2024

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1a

Phrases Containing hemisphere

• cerebral hemisphere
• eastern hemisphere
• northern hemisphere
• southern hemisphere
• western hemisphere

Kids Definition

hemisphere

noun

hemi·​sphere ˈhem-ə-ˌsfi(ə)r 

1

: one of the halves of the earth as divided by the equator or by a meridian

2

: one of two halves of a sphere

3

: cerebral hemisphere

Medical Definition

hemisphere

noun

hemi·​sphere -ˌsfi(ə)r 

: half of a spherical structure or organ: as

a

: cerebral hemisphere

b

: either of the two lobes of the cerebellum of which one projects laterally and posteriorly from each side of the vermis