/ sfɪə(r); NAmE sfɪr/ noun
1.
( geometry ) a solid figure that is completely round, with every point on its surface at an equal distance from the centre
2.
any object that is completely round, for example a ball
3.
an area of activity, influence or interest; a particular section of society
SYN domain :
the political sphere
This area was formerly within the sphere of influence of the US.
He and I moved in totally different social spheres.
4.
-sphere (in nouns) a region that surrounds a planet, especially the earth :
ionosphere
atmosphere
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WORD ORIGIN
Middle English : from Old French espere , from late Latin sphera , earlier sphaera , from Greek sphaira ball.