What characteristic distinguishes an equilateral triangle?

An equilateral triangle is specifically defined by the characteristic that all its sides are of equal length. This uniformity in side lengths also leads to all angles being equal, with each angle measuring 60 degrees. This unique property differentiates equilateral triangles from other types of triangles, such as isosceles triangles, which have at least two sides of the same length but do not require all three sides to be equal. The other options do not accurately capture the defining feature of an equilateral triangle, as they describe characteristics of other triangle types.