Which shape is defined as having only two parallel sides?

The shape characterized by having exactly two parallel sides is the trapezoid. This definition sets it apart from other geometric figures. A trapezoid features one pair of sides that runs parallel to each other, while the other pair can vary in length and are not parallel. This distinctive trait allows for a range of forms, including isosceles trapezoids (where the non-parallel sides are equal in length) and right trapezoids (with one right angle).

In contrast, a rectangle has two pairs of parallel sides and right angles at each corner, making it a more complex shape. A square, being a specific type of rectangle, also has two pairs of parallel sides but additionally requires all sides to be equal in length and all angles to be right angles. A parallelogram, similar to the rectangle, has two pairs of parallel sides, and opposite sides are equal in length. Thus, the trapezoid stands out as the shape that exclusively has one pair of parallel sides.