octagon
Americannoun
noun
Other Word Forms
Noun Inflected Forms
Etymology
Origin of octagon
1650–60; < Latin octagōnon < Greek oktágōnon, noun use of neuter of oktágōnos octangular; see octa-, -gon
Explanation
An octagon is a shape with eight sides. Picture a stop sign, and you'll get the idea. If your house is a strange, roundish shape with eight walls, it's an octagon, and if your medal for being the most improved bowler in your league has a shape with eight equal sides, it's also an octagon. You'll come across the word most often in geometry class, where you'll also learn that an octagon's eight interior angles always add up to 1080 degrees. The Greek root is oktagononos, "eight-angled," from okto, "eight," and gonia, "angle."
Vocabulary lists containing octagon
Geometry - Introductory
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UCPS 6th Grade Roots List #6
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Geometry (Base List)
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
There is a 600-ton octagon still sitting on the South Lawn.
From Salon • Jun. 15, 2026
Khabib Nurmagomedov, one of the best grapplers to ever set foot in the octagon, was set to compete for the lightweight belt.
From Slate • Jun. 14, 2026
Construction started late last month on a massive octagon with an open overhead dome and around 5,000 arena seats.
From Los Angeles Times • Jun. 9, 2026
Still, it’s better if the lidar knows the octagon is red.
From Barron's • May 4, 2026
It was a perfect octagon, the eight sides joined at the corners by rippling seams of silver.
From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
