Rectangle

In Euclidean plane geometry, a rectangle is a rectilinear convex polygon, or quadrilateral, with four right angles; equivalently it can be defined as an equiangular quadrilateral, since equiangular means all its angles are equal, or as a parallelogram containing a right angle. A rectangle with four sides of equal length is a square, and the term oblong is sometimes used for a rectangle that is not a square. The name comes from the Latin rectangulus, a combination of rectus, meaning right or proper, and angulus, meaning angle. A related figure, the crossed rectangle, is a self-intersecting quadrilateral formed from two opposite sides of a rectangle together with its two diagonals, and rectangles more generally appear throughout tiling problems, such as tiling the plane by rectangles or tiling a rectangle by other polygons.