octadecagon

O1C3T1A1D2E1C3A1G2O1N1

noun

A polygon with 18 sides and 18 vertices.

“A regular octadecagon cannot be constructed using a compass and straightedge.”

Similar
18-gon
Scrabble 17
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Meanings

nounoctadecagon (plural octadecagons)

plural octadecagons

  1. raregeometryA polygon with 18 sides and 18 vertices.

    A regular octadecagon cannot be constructed using a compass and straightedge.

    Synonyms: 18-gon

Synonyms & antonyms

nounA polygon with 18 sides and 18 vertices.

Similar
18-gon
Also see
18-gon

Origin

From octadeca- + -gon.

Full word history & related roots →

Translations

Bulgarian осемнадесетоъгълник
  • осемнадесетоъгълник (osemnadesetoăgălnik)geometry
Catalan octodecàgon
  • octodecàgongeometry
Chinese Mandarin 十八邊形 /十八边形
  • 十八邊形 /十八边形 (shíbā biānxíng)geometry
Czech osmnáctiúhelník
  • osmnáctiúhelníkgeometry
Dutch achttienhoek
  • achttienhoekgeometry
Esperanto dekoklatero
  • dekoklaterogeometry
Finnish 18-kulmio (kahdeksantoistakulmio)
  • 18-kulmio (kahdeksantoistakulmio)geometry
French octadécagone
  • octadécagonegeometry
German Achtzehneck
  • Achtzehneckgeometry
Greek δεκαοκτάγωνο
  • δεκαοκτάγωνο (dekaoktágono)geometry
Hungarian tizennyolcszög
  • tizennyolcszöggeometry
Italian ottadecagono
  • ottadecagonogeometry
Japanese 十八角形
  • 十八角形 (jūhachikakukei)geometry
Korean 십팔각형
  • 십팔각형 (sip'palgakhyeong)geometry
Polish osiemnastokąt
  • osiemnastokątgeometry
Portuguese octodecágono
  • octodecágonogeometry
Romanian octodecagon
  • octodecagongeometry
Russian восемнадцатиугольник
  • восемнадцатиугольник (vosemnadcatiugolʹnik)geometry
Spanish octodecágono
  • octodecágonogeometry
Swedish oktadekagon
  • oktadekagongeometry
Thai รูปสิบแปดเหลี่ยม
  • รูปสิบแปดเหลี่ยมgeometry
Turkish onsekizgen
  • onsekizgengeometry
Ukrainian вісімнадцятикутник
  • вісімнадцятикутник (visimnadcjatykutnyk)geometry
Cite this entry
APA

octadecagon. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/octadecagon

MLA

“octadecagon.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/octadecagon. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “octadecagon,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/octadecagon.

Source: octadecagon on Wiktionary, CC BY-SA 4.0.