Any topological space homeomorphic to the region in a plane between two concentric circles of different radius.
The ring of the sun not covered by the moon in an annular solar eclipse.
Structure in a fern that consists of differentially thick-walled cells on a sporangium that bend and distort as a result of drying.
A ring- or donut-shaped area or structure.
The region in a plane between two concentric circles of different radii.
The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom.
The space contained between the centre well bore and any external tubing. Sometimes used for separated gas flow.
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 .
The region in which something or someone is active; one's province, domain.
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 .
A spherical physical object; a globe or ball.
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).
The extension of a general conception, or the totality of the individuals or species to which it may be applied.
An area of activity for a planet; or by extension, an area of influence for a god, hero etc.
To place in a sphere, or among the spheres; to ensphere.
To make round or spherical; to perfect.