Enneagram (geometry)
In geometry, an enneagram is a nine-pointed geometric figure. The term derives from two Greek words: ennea (nine) and grammon (writ or draft).
Regular enneagrams
A regular enneagram (a nine-sided star polygon), is constructed using the same points as the regular enneagon but connected in fixed steps. It has two forms, represented by a Schläfli symbol as {9/2} and {9/4}, connecting every second and every fourth points respectively.
There is also a star figure, |9/3|, made from the regular enneagon points but connected as a compound of three equilateral triangles.[1][2] This last is sometimes also called a nonagram. This geometrical figure should not be confused with the logic puzzles called nonograms.
 Complete graph K9 |
 Enneagon {9/1} |
 Star polygon {9/2} |
 Star figure |9/3| |
 Star polygon {9/4} |
Use in popular culture
The heavy metal band, Slipknot, uses the |9/3| star figure nonagram as a symbol.
The nine-pointed star or nonagram symbolizes the Nine Fruits of the Spirit [1].
See also
References
- ^ Grünbaum, B. and G. C. Shephard; Tilings and Patterns, New York: W. H. Freeman & Co., (1987), ISBN 0-7167-1193-1.
- ^ Grünbaum, B.; Polyhedra with Hollow Faces, Proc of NATO-ASI Conference on Polytopes ... etc. (Toronto 1993), ed T. Bisztriczky et al, Kluwer Academic (1994) pp. 43-70.