# 13-sided solid nomenclature

**URL:** <https://boards.straightdope.com/t/13-sided-solid-nomenclature/384805>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [December 19, 2006, 6:19pm UTC](https://boards.straightdope.com/t/13-sided-solid-nomenclature/384805 "2006-12-19T18:19:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Kaisharga](https://avatars.discourse-cdn.com/v4/letter/k/7ba0ec/32.png) [@Kaisharga](https://boards.straightdope.com/u/Kaisharga)\
**Post date:** [December 19, 2006, 6:19pm UTC](https://boards.straightdope.com/t/13-sided-solid-nomenclature/384805/1 "2006-12-19T18:19:47Z")

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Link to the appropriate column follows: [http://www.straightdope.com/classics/a3\_252.html](http://www.straightdope.com/classics/a3_252.html)

I’m afraid I must correct. The suffix -gon denotes two-dimensional shapes, as in ‘pentagon’ or ‘octagon.’ When referring to three dimensional solids, the suffix appropriate to the situation becomes -hedron (sometimes seen pluralized as -hedra, though -hedrons is preferred). So we have nonhedrons (nine-sided solids), dodekahedrons (twenty-sided solids), and thus, triskaidekahedrons (thirteen-sided solids).

–Adam, linguistics student and die collector

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**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\
**Post date:** [December 19, 2006, 6:42pm UTC](https://boards.straightdope.com/t/13-sided-solid-nomenclature/384805/2 "2006-12-19T18:42:28Z")

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You may be a linguistics student, but you’re not much of geometer. The shape that the Susan B. Anthony dollar should be, but is not, is a triskaidecagonal cylinder; viewed face-on, it would be a triskaidecagon. If reckoned simply as a solid, it could be called a pentakaidecahedron, but that is less descriptive.

(Spelling such words with a “k” instead of a “c”, by the way, is good Greek, but decidedly minority English except in the metric prefix, which is officially “deka-” in the US, but “deca-” in the rest of the world.)