Which triangle classification includes at least one side that is longer than the other two?

The classification that includes at least one side longer than the other two is the scalene triangle. In a scalene triangle, all three sides are of different lengths, which directly means that at least one side will be longer than the remaining two sides. This characteristic is essential to the definition of a scalene triangle.

Equilateral triangles have all sides equal, so it does not fit the criteria of having one side longer than the others. Isosceles triangles have at least two sides that are equal in length, which also eliminates the possibility of one side being longer than both others. Right triangles are defined by having one angle that is 90 degrees, but that does not inherently mean that one side must be longer than the others—it can also be isosceles or scalene.

Thus, the scalene triangle's unique quality of having all sides of different lengths makes it the correct classification for a triangle with at least one side longer than the other two.