Enneagram (geometry)

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 nine-pointed plane figure. It is sometimes called a nonagram.

The name enneagram combines the numeral prefix, , with the Greek suffix . The -gram suffix derives from γραμμῆς (grammēs) meaning a line.

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.

The nine-pointed star or enneagram can also symbolize the nine gifts or fruits of the Holy Spirit.

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