equilateral

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adjective equi·lat·er·al \ ˌē-kwə-ˈla-tə-rəl , ˌe- , -ˈla-trəl \

Definition of equilateral

1 :having all sides equal
  • an equilateral triangle
  • an equilateral polygon
— see triangle illustration
2 :having all the faces equal
  • an equilateral polyhedron

Recent Examples of equilateral from the Web

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.

Did You Know?

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.

Origin and Etymology of equilateral

Late Latin aequilateralis, from Latin aequi- + later-, latus side — more at lateral

Other Mathematics and Statistics Terms



EQUILATERAL Defined for Kids

equilateral

play
adjective equi·lat·er·al \ ˌē-kwə-ˈla-tə-rəl , ˌe-kwə- \

Definition of equilateral for Students

:having all sides or faces equal
  • an equilateral triangle

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