Quadrilaterals are figures that have __________ straight sides.

A quadrilateral is defined as a polygon with four straight sides. This classification encompasses various shapes such as squares, rectangles, trapezoids, and parallelograms, all of which have four sides and the interior angles that add up to 360 degrees. The term "quadrilateral" actually derives from the Latin words "quadra," meaning four, and "latus," meaning side.

Understanding the properties that define quadrilaterals is crucial in various applications, including geometry, engineering, and architecture, as they often serve as foundational structures in designs and calculations. The other options do not apply since they exceed the definition of quadrilaterals, which specifically indicates four sides.