Which type of triangle has all sides of different lengths?

A triangle that has all sides of different lengths is classified as a scalene triangle. This is a fundamental type of triangle in geometry where not only are the lengths of all three sides unique, but consequently, all three angles are also different. This distinguishes scalene triangles from other types.

In contrast, an equilateral triangle has all three sides of equal length, meaning all sides are the same. An isosceles triangle has exactly two sides that are of equal length, which does not fit the criterion of all sides being different. While a right triangle can have different side lengths, it is defined specifically by having one angle of 90 degrees, and it can also be isosceles if it meets that condition. Thus, the defining characteristic of a scalene triangle holds true in this context, confirming its classification.