What attribute must be present for a quadrilateral to also be a trapezoid?

At least two of the opposite sides must be parallel.

Step-by-step explanation:

In the picture below, the segment AB must be parallel to the segment DC so that the figure can be called a trapezoid.

The main attribute a quadrilateral must have to also be a trapezoid is that it has a pair of parallel opposite sides.

Step-by-step explanation:

A quadrilateral is a polygon with four sides. The sum of its four interior angles must be equal to 360 °.

The trapezoids meet the above conditions but at least a couple of opposite sides must be parallel (two lines in a plane that do not intersect or touch each other at any point).

Special trapezoids are:

Square: both pairs of opposite sides are parallel and each interior angle is right. Each side has the same length.

Rectangle: both pairs of opposite sides are parallel and each interior angle is right. Each side has the same length.

Squares and rectangles are also consider parallelograms (both pairs of opposite sides are parallel).