Trapezoid

The trapezoid, or traz, is a quadrilateral with one pair of opposite parallel sides. It is a specific case of an irregular tetragon. All trapezoids are convex in Euclidean geometry.

Types of trapezoids
If the two non-parallel sides of a trapezoid intersect, the figure may more specifically be called a crossed trapezoid. If the two non-parallel sides have the same length, the figure may be called an isosceles trapezoid. If both conditions are met, the figure may be called a crossed isosceles trapezoid, or simply a butterfly.

An isosceles trapezoid with edge length ratios 2:1:1:1 is called a triamond, constructible as a blend of three equilateral triangles. Polyhedra containing triamonds have been studied, particularly the set of convex triamond polyhedra.