In geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, or right angles). It can also be defined as a rectangle in which two adjacent sides have equal length. A square with vertices ABCD would be denoted □ ABCD. The square is the n=2 case of the families of n-hypercubes and n-orthoplexes. [Square. Wikipedia]