What characterizes an equilateral triangle?

An equilateral triangle is characterized by having three congruent sides, meaning all sides are of equal length. This definition also implies that the angles opposite each side are equal, with each angle measuring 60 degrees. The property of equal sides leads to equal angles, which helps in reinforcing the essential characteristics of equilateral triangles in geometry.

In contrast, the other choices describe different types of triangles. A triangle with no congruent sides is defined as a scalene triangle, while a triangle with at least two congruent sides refers to an isosceles triangle. A triangle with three acute angles could apply to several types of triangles, including both equilateral and acute triangles, but does not uniquely identify the equilateral triangle. The unique feature of an equilateral triangle is the characteristic of having three equal sides.