The word "eleven-sided" refers to a polygon or shape with eleven sides. Synonyms for "eleven-sided" include "hendecagon," "undecagon," or "11-gon." In geometry, a hendecagon is a regular 11-sided polygon, meaning that all 11 sides are equal in length, and all 11 interior angles are congruent. The term "undecagon" is also used to describe an 11-sided polygon, but it is less commonly used than "hendecagon." The prefix "hendeca-" is derived from the Greek language, meaning "eleven." Some other synonyms for "eleven-sided" include "11-sided figure," "polygon with 11 sides," or "11-angular figure".