Enneagonal symmetry

Enneagonal symmetry, also known as ennic symmetry and notated as I2(9), is a 2D spherical Coxeter group. It is the symmetry group of the enneagon, with 9 rotation and 9 reflection elements.

Subgroups

 * I2(7)+ (maximal)
 * A2 (maximal)
 * A2+
 * A1×I
 * I×I

Convex polytopes with H2 symmetry

 * Enneagon (regular)
 * Dienneagon (isogonal)/Enneambus (isotopic)