In geometry, an enneagon or nonagon is a nine-sided polygon.
In geometry, the 120-cell, or hecatonicosachoron, is the convex, regular polychoron (a 4-dimensional polytope) with 120 cells (or facets).
See also: List of mathematical topics The word esoteric generally relates to that which is known only by a restricted number of people (contrast exoteric).