rectangles

A rectangle is a parallelogram with four right angles. In Euclidean geometry, it is a quadrilateral in which every interior angle measures 90 degrees. Consequently, opposite sides are parallel and equal in length.

Diagonals of a rectangle are equal in length and bisect each other, meeting at the figure’s center.

The area of a rectangle is the product of its adjacent side lengths, A = l × w, where l and w denote the lengths of adjacent sides. The base-height form also holds, A = base × height. The perimeter is P = 2(l + w).

A square is a rectangle with all sides equal; hence every square is a rectangle, but not every rectangle is a square. Every rectangle is a parallelogram, but a parallelogram is a rectangle only if it has right angles. Rectangles can be axis-aligned (with sides parallel to the axes) or rotated in the plane.

Rectangles appear in many contexts, including architecture, floor plans, and computer graphics. In graphics, images are often composed of many tiny rectangles (or pixels), and the rectangle serves as a basic building block for coordinate geometry and tiling.