Unduloid (onduloid)

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In geometry, a surface with constant nonzero mean curvature is known as an unduloid or onduloid. This surface can be obtained by rolling an ellipse along a fixed line and revolving the resulting curve around that line. In 1841, Delaunay proved that the only surfaces of revolution with constant mean curvature are those obtained by rotating the roulettes of conics. These include the plane, cylinder, sphere, catenoid, unduloid, and nodoid.