sphere

¹ American  

[sfeer] / sfɪər /

noun

1. Geometry.

   1. a solid geometric figure generated by the revolution of a semicircle about its diameter; a round body whose surface is at all points equidistant from the center. Equation: x 2 + y 2 + z 2 = r 2 .

   2. the surface of such a figure; a spherical surface.

2. any rounded body approximately of this form; a globular mass, shell, etc.

3. Astronomy.

   1. a planet or star; heavenly body.

   2. celestial sphere.

   3. any of the transparent, concentric, spherical shells, or layers, in which, according to ancient belief, the planets, stars, and other heavenly bodies were set.

4. the place or environment within which a person or thing exists; a field of activity or operation.

   to be out of one's professional sphere.

   Synonyms:

   domain, realm, compass, province, area, orbit

5. a particular social world, stratum of society, or walk of life.

   His social sphere is small.

   Synonyms:

   rank, class

6. a field of something specified.

   a sphere of knowledge.

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verb (used with object)

sphered, sphering

1. to enclose in or as if in a sphere.

2. to form into a sphere.

3. to place among the heavenly spheres.

-sphere ² American  

1. a combining form of sphere (planisphere ); having a special use in the names of the layers of gases and the like surrounding the earth and other celestial bodies (ionosphere ).

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sphere ¹ British  

/ sfɪə /

noun

1. maths

   1. a three-dimensional closed surface such that every point on the surface is equidistant from a given point, the centre

   2. the solid figure bounded by this surface or the space enclosed by it. Equation: ( x–a )² + ( y–b )² + ( z–c )² = r ², where r is the radius and ( a, b, c ) are the coordinates of the centre; surface area: 4π r ²; volume: 4π r ³/3

2. any object having approximately this shape; globe

3. the night sky considered as a vaulted roof; firmament

4. any heavenly object such as a planet, natural satellite, or star

5. (in the Ptolemaic or Copernican systems of astronomy) one of a series of revolving hollow globes, arranged concentrically, on whose transparent surfaces the sun (or in the Copernican system the earth), the moon, the planets, and fixed stars were thought to be set, revolving around the earth (or in the Copernican system the sun)

6. particular field of activity; environment

   that's out of my sphere

7. a social class or stratum of society

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verb

1. to surround or encircle

2. to place aloft or in the heavens

-sphere ² British  

combining form

1. having the shape or form of a sphere

   bathysphere

2. indicating a spherelike enveloping mass

   atmosphere

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sphere Scientific  

/ sfîr /

1. A three-dimensional geometric surface having all of its points the same distance from a given point.

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Other Word Forms

• -spheric combining form
• sphereless adjective
• spherelike adjective
• subsphere noun
• unsphering adjective

Etymology

Origin of sphere

1250–1300; < Late Latin sphēra, Latin sphaera globe < Greek sphaîra ball; replacing Middle English spere < Old French spere < Late Latin spēra, variant of sphēra

Explanation

Marbles, oranges, bubbles, and beach balls — all of these objects illustrate the shape of a sphere, or globe (unless the beach balls are under-inflated, in which case they’re sort-of a “squished-sphere” shape). Sphere is often used metaphorically to refer to a particular aspect or area of something. For example, unless you’re a trained circus performer, tightrope walking and fire swallowing probably lie outside of your sphere of expertise. Sphere frequently occurs in the phrase “sphere of influence,” which designates the geographical area over which a person, organization, or nation has control. In many households, whoever is in charge of the cooking controls the kitchen; so, the kitchen falls within his or her sphere of influence.

Example Sentences

Broad became one of LA.’s most influential civic leaders, using his multibillion-dollar fortune, political clout and forceful personality to spur advancements in the public sphere, particularly in the arts.

From Los Angeles Times • Apr. 14, 2026

“The approach is clear: maximum moral clarity in the public sphere, and the greatest possible dialogue in the halls of power,” he said.

From The Wall Street Journal • Apr. 10, 2026

Outside of the culinary sphere, tomatoes have also become something of a cultural icon, thanks to a “Tomato Girl” microtrend that took off in summer 2023.

From Salon • Apr. 6, 2026

The next major milestone is expected overnight Sunday into Monday, at which point the astronauts will enter the "lunar sphere of influence," where the Moon's gravity will have stronger pull on the spacecraft than Earth's.

From Barron's • Apr. 5, 2026

Pythagoras argued that the earth sat at the center of the universe, and the sun, moon, planets, and stars revolved around the earth, each pinned inside a sphere.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

Related Words

• circle
• field
• realm
• scope