equilateral
Americanadjective
noun
-
a figure having all its sides equal.
-
a side equivalent, or equal, to others.
adjective
noun
-
a geometric figure having all its sides of equal length
-
a side that is equal in length to other sides
Other Word Forms
Etymology
Origin of equilateral
From the Late Latin word aequilaterālis, dating back to 1560–70. See equi-, lateral
Explanation
A shape is equilateral if all the sides are the same length. In geometry class, people learn about many shapes, such as triangles and squares. A square is equilateral, because all of its sides are the same length. A rhombus is also equilateral — its sides are also the same length. A triangle can be equilateral too, but not a scalene triangle, which has three sides of different lengths. The word equal should help you remember what equilateral means. You can also use it as a noun for an equilateral shape.
Vocabulary lists containing equilateral
STAAR Grade 5 Mathematics: Geometry — Triangles, Polygons, and Prisms
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STAAR Grade 8 Mathematics: Geometry and Measurement, List 2
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Geometry, List 2
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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.
It’s easy to place three dots all the same distance from each other—just use an equilateral triangle.
From Slate ● Jun. 22, 2026
Lisa will use the same principle but fire its beams over a much greater distance, and between three identical spacecraft arranged as an equilateral triangle.
From BBC ● Jan. 25, 2024
She added an equilateral oval line, slightly off-center within the disk’s perfect circle.
From Los Angeles Times ● Jan. 6, 2023
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.
From Washington Post ● Dec. 2, 2022
Some pointed straight and high like an equilateral triangle and others were angled like a sail in the wind.
From "The Line Tender" by Kate Allen
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.
