apothem

noun

ap·​o·​them ˈa-pə-ˌthem 

: the perpendicular from the center of a regular polygon to one of the sides

Word History

Etymology

borrowed from French apothème, of uncertain origin

Note: The term is most likely based on a presumed Greek *apóthema or *apóthēma, a derivative of apotithénai "to put away, put aside" (perhaps taken to mean "to place to the side"), parallel to hypóthēma "base, stand," a derivative of hypotithénai "to put under" (see apothecary). It is undetermined who first used the word, which appears as apotheme in the expanded fourth edition (Paris, 1710) of the French priest and mathematician Bernard Lamy's Les elemens de geometrie (first edition 1685).

First Known Use

1813, in the meaning defined above