Monogon

In geometry a monogon is a polygon with one edge and one vertex. It has Schläfli symbol {1}. Since a monogon has only one side and only one vertex, every monogon is regular by definition.

In Euclidean geometry

In Euclidean geometry a monogon is a degenerate polygon because its endpoints must coincide, unlike any Euclidean line segment. Most definitions of a polygon in Euclidean geometry do not admit the monogon.

In spherical geometry

In spherical geometry, a monogon can be constructed as a vertex on a great circle (equator). This forms a dihedron, {1,2}, with two hemispherical monogonal faces which share one 360° edge and one vertex. Its dual, a hosohedron, {2,1} has two antipodal vertices at the poles, one 360 degree lune face, and one edge (meridian) between the two vertices.

Monogonal dihedron, {1,2}

Monohedral hosohedron, {2,1}

See also

• Digon

References

• Herbert Busemann, The geometry of geodesics. New York, Academic Press, 1955
• Coxeter, H.S.M; Regular Polytopes (third edition). Dover Publications Inc. ISBN 0-486-61480-8