Circle of the sphere

a circle upon the surface of the sphere, called a great circle when its plane passes through the center of the sphere; in all other cases, a small circle.

See also: Circle

References in periodicals archive ?
Supposing the eye placed in the centre of a sphere, every great circle of the sphere will have the same appearance to the eye as if it was a straight line.
Reid implies as much when he says "[A]ny line which is drawn in the plane of a great circle of the sphere, whether it be in reality straight or curve, will appear straight to the eye [placed at the centre of the sphere].