In Euclidean geometry, a **rhombus** (◊), plural **rhombi** or **rhombuses**, is a simple (non-self-intersecting) quadrilateral whose four sides all have the same length. Another name is **equilateral quadrilateral**, since equilateral means that all of its sides are equal. The rhombus is often called a **diamond**, after the diamonds suit in playing cards, or a **lozenge**, though the latter sometimes refers specifically to a rhombus with a 45° angle.

Every rhombus is a parallelogram, and a rhombus with right angles is a square. (Euclid's original definition and some English dictionaries' definition of rhombus excludes squares, but modern mathematicians prefer the inclusive definition.)

Read more about Rhombus: Etymology, Characterizations, Basic Properties, Area, Inradius, Dual Properties, Other Properties