Rectangular

Rectangular is an adjective used to describe things that have the form of a rectangle or relate to a rectangle. In geometry, a rectangle is a quadrilateral with four right angles; its opposite sides are parallel and equal in length, and the diagonals are equal and bisect each other.

In two dimensions, the area of a rectangle is the product of its length and width (A = l × w), and its perimeter is P = 2(l + w). The diagonal length is d = sqrt(l^2 + w^2). Rectangular shapes are common in everyday objects such as screens, books, and windows, reflecting the practical utility of right angles in design and construction.

A three-dimensional extension is the rectangular prism (also called a rectangular parallelepiped), which has six rectangular faces. Its volume is V = l × w × h, and its surface area is SA = 2(lw + lh + wh). Rectangular prisms are a basic model in architecture, packaging, and many engineering calculations.

Rectangular coordinates, often called Cartesian coordinates, describe positions in a plane or space using perpendicular axes (such as x, y, and z). The rectangular grid underpins many measurement, mapping, and computer graphics systems, enabling straightforward computation of distances, areas, and volumes.

Etymology and usage: rectangular comes from Latin rectangulus, from rectus (upright) and angulus (angle). In general language, it denotes anything with or relating to the shape of a rectangle. In mathematics, it also distinguishes non-square configurations, such as rectangular matrices that have a different number of rows and columns.