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>
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 (manysided 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 equalsided. The standard polyhedrons (manysided 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
First Known Use: 1570
Other Mathematics and Statistics Terms
EQUILATERAL Defined for Kids
equilateral
playDefinition of equilateral for Students
: having all sides or faces equal <an equilateral triangle>
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Spanish Central: Translation of equilateral Nglish: Translation of equilateral for Spanish speakers
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