A quadrilateral with four congruent sides and congruent opposite angles.

### Properties

- Rhombuses belong to the class of parallelograms; they are parallelograms with four congruent sides.
- The two diagonals of a rhombus are perpendicular.
- The opposite sides of a rhombus are parallel.
- A rhombus has two axes of symmetry.

Based on its properties, a rhombus belongs to the family of convex quadrilaterals, trapezoids and parallelograms.

### Formulas

The perimeter *P* of a rhombus with side length *c* is given by : \(P=4c\).

The area *A* of a rhombus with a short diagonal \(d\) and a long diagonal \(D\) is given by : \(A=frac{Dtimes d}{2}\)