A ring- or donut-shaped area or structure.
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.
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.
Any topological space homeomorphic to the region in a plane between two concentric circles of different radius.
Any spherical (or nearly spherical) object.
The planet Earth.
A circular military formation used in Ancient Rome, corresponding to the modern infantry square.
A spherical model of Earth or other planet.
A land snail of the genus Mesodon
A light bulb.
A woman's breast.
To become spherical.
To make spherical.