The Collaborative International Dictionary
Dihedron \Di*he"dron\, n. [See Dihedral.]
A figure with two sides or surfaces.
--Buchanan.
Wikipedia
A dihedron is a type of polyhedron, made of two polygon faces which share the same set of edges. In three-dimensional Euclidean space, it is degenerate if its faces are flat, while in three-dimensional spherical space, a dihedron with flat faces can be thought of as a lens, an example of which is the fundamental domain of a lens space L(p,q).
Usually a regular dihedron is implied (two regular polygons) and this gives it a Schläfli symbol as {n,2}. Each polygon fills a hemisphere, with a regular n-gon on a great circle equator between them.
The dual of a n-gonal dihedron is the n-gonal hosohedron, where n digon faces share two vertices.
Usage examples of "dihedron".
Le Cagot would now be at the most difficult feature of the ascent, a double dihedron at meter point 44.
Just below the double dihedron was a narrow ledge where one could get purchase for the first jackknife squeeze, a maneuver hard enough for a man with two good arms, consisting of chimney climbing so narrow in places that all one could get was a heel-and-knee wedge, so wide in others that the wedge came from the flats of the feet to the back of the neck.
Once past the double dihedron, his weight could be taken on the cable and be could be dragged up like a sack of millet.
A fresh battery could drive the little bulb day and night for four days and, if necessary, could be sent up, now that they had widened the bottleneck and double dihedron, to be recharged from the pedal-driven magneto that kept their telephone battery fresh.
Unnerving, because Hel was now totally dependent on the cable, after ninety minutes of negotiating the narrow, twisting shaft with its bottlenecks, narrow ledges, tricky dihedrons, and tight passages down which he had to ease himself gingerly, never surrendering to gravity because the cable was slack to give him maneuvering freedom.
Le Cagot, a bull of strength and endurance despite his fifty years, always went down first, sweeping up as he made his slow descent, clearing ledges and dihedrons of loose rock and rubble that could be knocked off by the cable and kill a man in the shaft.
He would be at me ledge, tilting back his head and looking up at the lower of the two dihedrons in the beam of his helmet lamp.
Unnerving, because Hel was now totally dependent on the cable, after ninety minutes of negotiating the narrow, twisting shaft with its bottlenecks, narrow ledges, tricky dihedrons, and tight passages down which he had to ease himself gingerly, never surrendering to gravity because the cable was slack to give him maneuvering freedom.