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Nine-pointed star polygon From Wikipedia, the free encyclopedia
In geometry, an enneagram (🟙 U+1F7D9) is a nine-pointed plane figure. It is sometimes called a nonagram, nonangle, or enneagon.[1]
Enneagram | |
---|---|
![]() Enneagrams shown as sequential stellations | |
Edges and vertices | 9 |
Symmetry group | Dihedral (D9) |
Internal angle (degrees) | 100° {9/2} 20° {9/4} |
The word 'enneagram' combines the numeral prefix ennea- with the Greek suffix -gram. The gram suffix derives from γραμμῆ (grammē) meaning a line.[2]
A regular enneagram is a 9-sided star polygon. It is constructed using the same points as the regular enneagon, but the points are connected in fixed steps. Two forms of regular enneagram exist:
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.[3][4] (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.[5]
Compound | Regular star | Regular compound |
Regular star |
---|---|---|---|
![]() Complete graph K9 |
![]() {9/2} |
![]() {9/3} or 3{3} |
![]() {9/4} |
![]() The final stellation of the icosahedron has 2-isogonal 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 nine-pointed star |
![]() A 9/3 enneagram |
The nine-pointed star or enneagram can also symbolize the nine gifts or fruits of the Holy Spirit.[6]