Final answer:
A shape with 4 sides and exactly 1 pair of parallel sides is called a trapezoid (American English) or trapezium (British English).
Step-by-step explanation:
A shape that has 4 sides and exactly 1 pair of parallel sides is best named a trapezoid in American English, or a trapezium in British English. This geometric figure is defined by having a pair of sides that are parallel, known as the bases, while the other two sides may or may not be of equal length and are not parallel to each other. The non-parallel sides are called the legs of the trapezoid. If the legs of the trapezoid are of equal length, it is also known as an isosceles trapezoid. When discussing shapes with four sides, we often mention other quadrilaterals like squares, rectangles, and parallelograms, but the defining characteristic of a trapezoid is that one and only one pair of sides is parallel.