decagon

American  

[dek-uh-gon, -guhn] / ˈdɛk əˌgɒn, -gən /

noun

Geometry.

• decagons
  plural

1. a polygon having ten angles and ten sides.

---

decagon British  

/ ˈdɛkəˌɡɒn /

noun

1. a polygon having ten sides

---

decagon Scientific  

/ dĕk′ə-gŏn′ /

1. A polygon having ten sides.

---

Other Word Forms

Derived Forms

• decagonal
  adjective
• decagonally
  adverb

Inflected Forms

Nouns

• decagons
  plural

---

Etymology

Origin of decagon

From the Medieval Latin word decagōnum, dating back to 1565–75. See deca-, -gon

---

Explanation

A decagon is a closed shape with ten sides and ten angles. Your geometry teacher would also tell you that a decagon is a polygon. The word decagon comes from Greek roots, deka, or "ten," and gōnia, "angle or corner." Any ten-sided shape can be called a decagon, whether it's a street sign or the doodle you draw in your notebook during math class. Speaking of math class, in geometry you may learn that a "regular decagon" is one with sides that are all equal to each other and with internal angles that all measure 144 degrees.

Example Sentences

See Examples For:

decagon decagons

Scientists still do not know what triggered the decagon or whether it will remain stable.

From Science Daily ● Sep. 3, 2026

Ground-based observations collected in 2025 provided stronger evidence that the feature had developed into a decagon.

From Science Daily ● Sep. 3, 2026

Different wavelengths allow astronomers to observe different altitudes within Saturn's atmosphere, producing small shifts in where the decagon seems to appear.

From Science Daily ● Sep. 3, 2026

Researchers will continue monitoring Saturn to see whether the southern decagon becomes a stable, long-lived feature like the northern hexagon or keeps changing.

From Science Daily ● Sep. 3, 2026

Most of the list came from the state eighth grade curriculum: barometer, decagon, perpendicular .

From "Schooled" by Gordon Korman

Of nouns in on, derived from Greek, the greater part always form the plural regularly; as, etymons, gnomons, ichneumons, myrmidons, phlegmons, trigons, tetragons, pentagons, hexagons, heptagons, octagons, enneagons, decagons, hendecagons, dodecagons, polygons.

From The Grammar of English Grammars by Goold Brown

A. Because it has ten sides and ten angles, and there are both regular and irregular decagons.

From The Infant System For Developing the Intellectual and Moral Powers of all Children, from One to Seven years of Age by Samuel Wilderspin

Random Word

Spin the wheel and learn a new word!

---