A four-sided figure with no parallel sides is commonly referred to as a trapezium (or trapezoid, in some regions). Unlike a rectangle or a parallelogram, where at least one pair of opposite sides is parallel, a trapezium has all sides of different lengths without any parallel pairs.
This unique structure means that the angles and the lengths of the sides can vary widely, giving it a more irregular appearance compared to other quadrilaterals. Each trapezium can take on a different shape depending on the lengths of its sides and the measures of its angles, leading to a diverse category of figures under the trapezium classification.