The term "rectangular" refers to a shape that has four sides and four right angles, typically seen in objects like tables, books, and screens. A rectangle's opposite sides are equal in length, making it a specific type of quadrilateral. Rectangles can vary in size and proportion, leading to different types such as squares, which are rectangles with equal side lengths. The area of a rectangle is calculated by multiplying its length by its width, while the perimeter is the total distance around the shape, found by adding the lengths of all four sides.