What defines an equilateral triangle?

An equilateral triangle is defined by having three congruent sides, meaning all three sides of the triangle are of equal length. This characteristic ensures that not only are the sides equal, but the angles opposite each side must also be equal, with each angle measuring 60 degrees. This congruence in sides and angles gives the equilateral triangle its symmetrical properties.

While the option stating that a triangle has three equal angles aligns with the properties of an equilateral triangle, the defining characteristic is the equal lengths of the sides. The presence of one right angle defines a right triangle, and a triangle with no equal sides is referred to as a scalene triangle. Thus, the best definition of an equilateral triangle focuses specifically on the congruence of the sides.