A sphere (frae Greek σφαῖρα — sphaira, "globe, baw") is a perfectly roond geometrical an circular object in three-dimensional space that resembles the shape o a completely roond baw. Lik a circle, which, in geometrical contexts, is in twa dimensions, a sphere is the set o pynts that are aw the same distance r frae a gien pynt in space. This distance r is the radius o the sphere, an the gien pynt is the center o the sphere. The maximum straucht distance throu the sphere passes throu the centre an is sicweys twice the radius; it is the diameter.
In mathematics, a distinction is made atween the sphere (a twa-dimensional closed surface embeddit in three-dimensional Euclidean space) an the baw (a three-dimensional shape that includes the interior o a sphere).
- σφαῖρα, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus