How are equilateral triangles defined?

Equilateral triangles are defined specifically by the property that all three sides are of equal length. This characteristic sets equilateral triangles apart, as it ensures that not only are the sides equal, but the angles opposite those sides are also equal, each measuring 60 degrees. This uniformity contributes to the triangle's symmetry and balances.

In contrast, the other definitions provided do not accurately describe equilateral triangles. They may describe different types of triangles or contain inaccuracies, but the defining feature of an equilateral triangle hinges exclusively on the equality of its sides. Thus, recognizing that all three sides are equal is fundamental to understanding what constitutes an equilateral triangle.