Editing Rectangle (section)

===Traditional hierarchy===
A rectangle is a special case of a [[parallelogram]] in which each pair of adjacent [[Edge (geometry)|sides]] is [[perpendicular]].

A parallelogram is a special case of a trapezium (known as a [[trapezoid]] in North America) in which ''both'' pairs of opposite sides are [[Parallel (geometry)|parallel]] and [[equality (mathematics)|equal]] in [[length]].

A trapezium is a [[Convex polygon|convex]] [[quadrilateral]] which has at least one pair of [[parallel (geometry)|parallel]] opposite sides.

A convex quadrilateral is
* '''[[Simple polygon|Simple]]''': The boundary does not cross itself.
* '''[[Star-shaped polygon|Star-shaped]]''': The whole interior is visible from a single point, without crossing any edge.