چنبره

Also known as tori, doughnut shape

thumb|A ring torus with a selection of circles on its surface thumb|As the distance from the axis of revolution decreases, the ring torus becomes a horn torus, then a spindle torus, and finally degeneracy (mathematics)|degenerates into a double-covered [[sphere.]] thumb|A ring torus with aspect ratio 3, the ratio between the diameters of the larger (blue) circle and the smaller (red) circle. The two radii coordinates are shown as well. The radius denoted by capital, R, is the distance from the geometric center of the outer ring lying outside the volume, to the center of the inner ring. The rad