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Enneagram  

Enneagrams shown as sequential stellations


Edges and vertices  9 
Symmetry group  Dihedral (D9) 
Internal angle (degrees)  100° {9/2} 20° {9/4} 
In geometry, an enneagram is a ninepointed plane figure. It is sometimes called a nonagram.
The name enneagram combines the numeral prefix, ennea, with the Greek suffix gram. The gram suffix derives from γραμμῆς (grammēs) meaning a line.^{[1]}
A regular enneagram (a ninesided 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.^{[2]}^{[3]} (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.^{[4]}
Compound  Regular star  Regular compound 
Regular star 

Complete graph K_{9} 
{9/2} 
{9/3} or 3{3} 
{9/4} 
The final stellation of the icosahedron has 2isogonal enneagram faces. It is a 9/4 wound star polyhedron, but the vertices are not equally spaced. 
The Fourth Way teachings and the Enneagram of Personality use an irregular enneagram consisting of an equilateral triangle and an irregular hexagram based on 142857. 
The Bahá'í ninepointed star 
The ninepointed star or enneagram can also symbolize the nine gifts or fruits of the Holy Spirit.^{[5]}
Bibliography