In geometry, a rectangle is defined as a quadrilateral where all four of its angles are right angles. A rectangle with vertices ABCD would be denoted as ABCD.
From this definition, it follows that a rectangle has two pairs of parallel sides; that is, a rectangle is a parallelogram. An equilateral rectangle is known as a square.
Normally, of the two opposite pairs of sides in a rectangle, the length of the longer side is called the length of the rectangle, and the length of the shorter side is called the width.