Which triangle is defined as having no equal sides?

A triangle that is defined as having no equal sides is called a scalene triangle. In a scalene triangle, all three sides are of different lengths, which also means that all three interior angles are different. This distinction highlights the uniqueness of each side and angle in the triangle's structure, making scalene triangles distinct from equilateral and isosceles triangles.

Equilateral triangles have all sides of equal length, and isosceles triangles have at least two sides that are equal. An obtuse triangle, on the other hand, relates to the angles of the triangle rather than the lengths of its sides; it has one angle that measures greater than 90 degrees, but this definition does not pertain to the equality of the triangle's sides. Therefore, the correct identification of a triangle with no sides equal is the scalene triangle.