Edges and vertices 9 Internal angle (degrees) 100° {9/2}20° {9/4} | Symmetry group Dihedral (D9) | |
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In geometry, an enneagram is a nine-pointed plane figure. It is sometimes called a nonagram.
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The name enneagram combines the numeral prefix, ennea-, with the Greek suffix -gram. The -gram suffix derives from γραμμῆς (grammēs) meaning a line.
Regular enneagram
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} or 3{3}, made from the regular enneagon points but connected as a compound of three equilateral triangles. (If the triangles are alternately interlaced, this results in a Brunnian link.) This star figure is sometimes known as the star of Goliath, after {6/2} or 2{3}, the star of David.
This geometrical figure should not be confused with the logic puzzles called nonograms.
Other enneagram figures
The nine-pointed star or enneagram can also symbolize the nine gifts or fruits of the Holy Spirit.