What does decagonal mean?
"Decagonal" is an adjective describing anything that has ten sides and ten angles — in other words, anything shaped like a decagon. The word derives from the Greek deka, meaning ten, combined with gōnia, meaning angle, and it belongs to a whole family of geometric adjectives built on the same pattern, such as hexagonal, octagonal, and pentagonal. It is most at home in technical and descriptive contexts: mathematicians speak of decagonal prisms and decagonal tilings, architects may design decagonal towers or pavilions, and designers describe decagonal coins, tables, or tiles. Because it is precise and visual, it is useful whenever a plain phrase like "ten-sided" would feel clumsy or repetitive. While rare in casual conversation, the word is transparent once its parts are understood, making it an easy and satisfying addition to any vocabulary concerned with shapes, symmetry, and structure.
adjectiveHaving ten sides and ten angles; shaped like or relating to a decagon.
- Of a plane figure or solid: having ten sides and ten angles; shaped like a decagon.
"The courtyard featured a striking decagonal fountain at its center."
"The architect designed a decagonal tower that caught the light differently from every angle."
"Each decagonal tile was cut precisely so that ten tiles met perfectly at the room's center point."
The word comes from the Greek deka (ten) plus gōnia (angle) — so every time you say "decagonal," you're speaking ancient geometry out loud.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of decagonal
"Decagonal" traces back to the Greek deka ("ten") and gōnia ("angle"), the same root that gives English "polygon." The noun "decagon" entered English via Latin deca- forms during the Renaissance revival of classical geometry, and the adjective followed as a natural derivation. It shares its numeric root with "decade" and "decimal," all ultimately reflecting the Greek and Latin element for ten.
Related word forms
How decagonal is actually used
A technical term used chiefly in mathematics, geometry, architecture, and design writing. It is formal rather than conversational; in everyday speech people more often say "a ten-sided shape." It appears almost exclusively attributively (before a noun), as in "a decagonal prism."
Easily confused with decagonal
"Decagon" is the noun naming the ten-sided figure itself, while "decagonal" is the adjective describing something that has that shape.
"Decimal" relates to the number ten as a base for counting (base-10), whereas "decagonal" specifically describes a ten-sided geometric form.