A plane figure consisting of four points, each of which is
joined to two other points by a line segment. A quadrangle may be concave
or convex depending on whether the line segments
do or don't intersect. A convex quadrangle is a quadrilateral.
The word is from the Latin quadrangulum for four-cornered and is
also used to describe a rectangular area surrounded on all four sides by
buildings, or to such buildings themselves.
| Magdalen College, Oxford, quadrangle