| Rectangle | |
|---|---|
 Rectangle | |
| Type | quadrilateral, trapezium, parallelogram, orthotope |
| Edges and vertices | 4 |
| Schläfli symbol | { } × { } |
| Coxeter–Dynkin diagrams |   |
| Symmetry group | Dihedral (D2), [2], (*22), order 4 |
| Properties | convex, isogonal, cyclic Opposite angles and sides are congruent |
| Dual polygon | rhombus |
In Euclidean plane geometry, a rectangle is a rectilinear convex polygon or a quadrilateral with four right angles. It can also be defined as: an equiangular quadrilateral, since equiangular means that all of its angles are equal (360°/4 = 90°); or a parallelogram containing a right angle. A rectangle with four sides of equal length is a square. The term "oblong" is used to refer to a non-square rectangle.[1][2][3] A rectangle with vertices ABCD would be denoted as 
ABCD.
The word rectangle comes from the Latin rectangulus, which is a combination of rectus (as an adjective, right, proper) and angulus (angle).
A crossed rectangle is a crossed (self-intersecting) quadrilateral which consists of two opposite sides of a rectangle along with the two diagonals[4] (therefore only two sides are parallel). It is a special case of an antiparallelogram, and its angles are not right angles and not all equal, though opposite angles are equal. Other geometries, such as spherical, elliptic, and hyperbolic, have so-called rectangles with opposite sides equal in length and equal angles that are not right angles.
Rectangles are involved in many tiling problems, such as tiling the plane by rectangles or tiling a rectangle by polygons.
- ^ Tapson, Frank (July 1999). "A Miscellany of Extracts from a Dictionary of Mathematics" (PDF). Oxford University Press. Archived from the original (PDF) on 2014-05-14. Retrieved 2013-06-20.
- ^ "Definition of Oblong". Math Is Fun. Retrieved 2011-11-13.
- ^ Oblong – Geometry – Math Dictionary. Icoachmath.com. Retrieved 2011-11-13.
- ^ Coxeter, Harold Scott MacDonald; Longuet-Higgins, M.S.; Miller, J.C.P. (1954). "Uniform polyhedra". Philosophical Transactions of the Royal Society of London. Series A. Mathematical and Physical Sciences. 246 (916). The Royal Society: 401–450. Bibcode:1954RSPTA.246..401C. doi:10.1098/rsta.1954.0003. ISSN 0080-4614. JSTOR 91532. MR 0062446. S2CID 202575183.