Parallelsided

Parallelsided is an informal geometric term used to describe a polygon that has at least one pair of parallel sides. It is not a formal classification in Euclidean geometry, but it appears in some educational materials to emphasize the presence of parallelism without assigning the shape to a more specific category.

Because parallelism is the defining feature, a parallelsided polygon can have any number of sides, although triangles cannot be parallelsided since their sides cannot be parallel. The concept is most commonly applied to quadrilaterals: a trapezoid is a quadrilateral with exactly one pair of parallel sides, while a parallelogram has two pairs of parallel sides. In polygons with more sides, parallel sides may occur in various configurations; for example, a regular hexagon has three pairs of parallel sides.

In formal geometry, the term parallelsided is not a substitute for established classifications, but it helps describe a polygon when the sole focus is on the presence of parallelism. Consequently, all parallelograms, rectangles, rhombuses, and squares are also parallelsided, as they possess parallel sides by definition, while polygons that lack any parallel sides would not be described this way.

Usage and etymology: Parallelsided is used descriptively in some textbooks and online resources to highlight the property of parallelism without committing to a specific subtype. It serves as a convenient shorthand in discussions about polygons where parallel sides are the key feature. See also: parallelogram, trapezoid, parallelism.