In which type of trapezoid are the non-parallel sides congruent?

An isosceles trapezoid is characterized by having a pair of non-parallel sides that are congruent, meaning they are of equal length. This property distinguishes the isosceles trapezoid from other types of trapezoids. In addition to the congruent non-parallel sides, the angles adjacent to each base of an isosceles trapezoid are also congruent, adding to its symmetrical properties.

In contrast, a right trapezoid has one of its angles as a right angle, but does not necessarily have congruent non-parallel sides. A scalene trapezoid has sides of different lengths, meaning no sides are congruent. An equilateral trapezoid is not a standard classification in trapezoids, as it would imply a trapezoid with all sides equal, which is not a typical property of trapezoids.

Thus, the defining feature of the isosceles trapezoid makes it the correct answer to the question, as it uniquely possesses congruent non-parallel sides.