A rectangle is a simple shape that is characterized by having four sides at 90-degree angles to each other, and having both sets of opposing sides be the same length. Note that if all sides are equal to each other, the shape is not a rectangle, but a square.
A rectangle is one of the most common four sided two-dimensional shapes. It has both a length and a width dimension. Other four-sided shapes include squares, parallelograms and rhombuses. The area of a rectangle can be calculated by multiplying the length by the width while the perimeter can be calculated by adding up all the side lengths.