sphere

Etymology

From Middle English spere, from Old French sphere, from Late Latin sphēra, earlier Latin sphaera (“ball, globe, celestial sphere”), from Ancient Greek σφαῖρα (sphaîra, “ball, globe”), of unknown origin. Not related to superficially similar Persian سپهر (sepehr, “sky”) .

noun

1. (mathematics) A regular three-dimensional object in which every cross-section is a circle; the figure described by the revolution of a circle about its diameter .
2. A spherical physical object; a globe or ball.
   So your orientation changes a little bit but it sinks in that the world is a sphere, and you're going around it, sometimes under it, sideways, or over it. 6 July 2011, Piers Sellers, The Guardian
3. (astronomy, now rare) The apparent outer limit of space; the edge of the heavens, imagined as a hollow globe within which celestial bodies appear to be embedded.
   Though cold and darkness longer hang somewhere, / Yet Phoebus equally lights all the Sphere. 1635, John Donne, His parting form her
   Resistless rolls the illimitable sphere, / And one great circle forms the unmeasured year. 1791, Erasmus Darwin, The Economy of Vegetation, J. Johnson, page 190
4. (historical, astronomy, mythology) Any of the concentric hollow transparent globes formerly believed to rotate around the Earth, and which carried the heavenly bodies; there were originally believed to be eight, and later nine and ten; friction between them was thought to cause a harmonious sound (the music of the spheres).
   They understood not the motion of the eighth sphear from West to East, and so conceived the longitude of the Stars invariable. 1646, Thomas Browne, Pseudodoxia Epidemica, I.6
5. (mythology) An area of activity for a planet; or by extension, an area of influence for a god, hero etc.
6. (figurative) The region in which something or someone is active; one's province, domain.
   They thought – originally on grounds derived from religion – that each thing or person had its or his proper sphere, to overstep which is ‘unjust’. 1946, Bertrand Russell, History of Western Philosophy, I.20
7. The natural, normal, or proper place (of something).
8. An area or range over or within which someone or something exists, or has influence or significance.
9. (geometry) The set of all points in three-dimensional Euclidean space (or n-dimensional space, in topology) that are a fixed distance from a fixed point .
10. (logic, dated) The domain of reference of a proposition, subject, or predicate, or the totality of the particular subjects to which it applies.
    In point of fact, so often as we think a subject as partially included within the sphere of a predicate, eo ipso we think it as partially, that is, particularly, excluded therefrom. a. 1856, William Hamilton, “Appendix III: Quantification of Predicate,—Immediate Inference,—Conversion,—Opposition”, in Lectures on Metaphysics and Logic, volume 2, published 1860, page 526
    All categorical propositions necessarily imply the existence of their subjects in the appropriate sphere; in affirmative propositions this involves the existence of the predicate in the same sphere; but in negative propositions the predicate does not necessarily exist in that particular sphere, though it does in some sphere. 1896, James Welton, A Manual of Logic, 2nd edition, volume 1, page 213
    Finally, the disjunctive judgment contains a relation of two or more propositions to each other—a relation not of consequence, but of logical opposition, in so far as the sphere of the one proposition excludes that of the other. 1900 [1781], Immanuel Kant, translated by J. M. D. Meiklejohn, Critique of Pure Reason, page 58

verb

1. (transitive) To place in a sphere, or among the spheres; to ensphere.
2. (transitive) To make round or spherical; to perfect.