# rhombus

A rhombus is a quadrilateral in which both pairs
of opposite sides are parallel and all sides are the same length, that is,
an equilateral parallelogram. A rhombus
is also sometimes called a **rhomb** or a diamond. A rhombus
whose acute angles are 45° is called a **lozenge**. The diagonals *p* and *q* of a rhombus are perpendicular and satisfy the relationship *p*^{2} + *q*^{2} = 4*a*^{2}. The
area of a rhombus is given by *A* = ½ *pq*.