A parallelogram will be considered as Rhombus, when two adjacent sides are equal. In the figure, ABCD is a parallelogram, in which AB = AD. So, it is a Rhombus. A Rhombus has all the properties of a parallelogram. It also has the following additional properties.

Property.1) All the sides of a Rhombus are equal in length

In the figure, AB = BC = CD = DA

Property.2) The two diagonals of a Rhombus are perpendicular to each other

 In the figure, AC ⊥ BD

Property.3) Each diagonal of a rhombus bisects the angles at the two vertices it joins.

In the figure, AC bisects ∠A and ∠C and BD bisects ∠B and ∠D

Property.4) The diagonal of a Rhombus form four congruent triangles.

In the figure, ∆ OAB ≅ ∆ OBC ≅ ∆ OCD ≅ ∆ ODA