A rhombus is a four-sided figure with opposite sides parallel, making it a parallelogram. The rhombus differs from other parallelograms in that all four sides are equal in length.
While often referred to as a diamond, the angles of a rhombus can vary greatly. If the angles are equal to 90 degrees, the rhombus is a square. The special properties of a rhombus provide specific ways to determine if a figure fits its definition. Parallelograms with two equal-length consecutive sides are a rhombi, as are parallelograms with diagonal perpendiculars. According to Euclidian geometry, if either diagonal of a parallelogram bisects its interior angle, it is a rhombus.