equilateral
adjective
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Since equi- means "equal", the meaning of equilateral is easy to guess from its roots. The word is mostly used in geometry. The standard polygons (many-sided geometrical shapes)—the pentagon, hexagon, octagon, etc.—are assumed to be equilateral if we don't say otherwise; an equilateral rectangle has the special name square. But triangles are particularly important, and many triangles are not equal-sided. The standard polyhedrons (many-sided solids) are also equilateral. Most common is the cube, all of whose sides are square. The tetrahedron has four triangular sides and thus is a pyramid with a triangular base, unlike the pyramids of Egypt with their square bases.
Examples of equilateral in a Sentence
Sofia Celeste, Footwear News, 10 Apr. 2025
Each Magna-Tile is a translucent geometric shape, and this set includes squares (four large, 50 small) and triangles (11 right, 20 equilateral, and 15 isosceles).
—Katrina Cossey, Parents, 12 July 2023
The set includes 48 regular squares, eight large squares, eight thick-sided squares, eight squares that look like windowpanes, 16 small and 16 large equilateral triangles plus 16 isosceles triangles.
—Jessica Hartshorn, Good Housekeeping, 19 Dec. 2022
The equilateral cross with its legs bent at right angles is a millennia-old sacred symbol in Hinduism, Buddhism and Jainism that represents peace and good fortune.
—Arkansas Online, 28 Nov. 2022
See All Example Sentences for equilateral
Cite this Entry
“Equilateral.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/equilateral. Accessed 10 Sep. 2025.
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equilateral
adjective
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