Which shape can also be classified as a rectangle or rhombus?

A square is a unique shape that meets the criteria of being classified as both a rectangle and a rhombus. By definition, a rectangle is a quadrilateral with four right angles, while a rhombus is a quadrilateral with all four sides of equal length. A square possesses both traits: all four sides are equal in length, which aligns with the properties of a rhombus, and it has four right angles, which aligns with the properties of a rectangle.

This means a square can be viewed through the lens of both shapes, showcasing its distinct position in geometry where it satisfies the conditions for multiple classifications. Consequently, among the given options, the square is the only shape that can accurately be classified as both a rectangle and a rhombus.