Definition of equilateral
- an equilateral triangle
- an equilateral polygon
- an equilateral polyhedron
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'equilateral.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
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.
What made you want to look up equilateral? Please tell us where you read or heard it (including the quote, if possible).
of yeast or being unsettled or frivolous
Get Word of the Day daily email!
Merriam-Webster's New Words Quiz—Fall 2017 Edition!
Test your vocabulary with our 10-question quiz!TAKE THE QUIZ
Test Your Knowledge - and learn some interesting things along the way.TAKE THE QUIZ