High Quality Content by WIKIPEDIA articles! In geometry, a truncation is an operation in any dimension that cuts polytope vertices, creating a new facet in place of each vertex. A truncated n-sided polygon will have 2n sides (edges). A regular polygon uniformly truncated will become another regular polygon: t{n} is {2n}. Star polygons can also be truncated. A truncated pentagram {5/2} will look like a pentagon, but is actually a double-covered (degenerate) decagon with two sets of overlapping vertices and edges.