When can a quadrilateral also be called a rhombus?

When it has the properties of a rhombus, a quadrilateral can be called "rhombus" (It sides must be equal in lenght, its opposite sides must be parallel, its opposite angles must be equal, its diagonals must be perpendicular and bisect each other).

Step-by-step explanation:

It is important the remember that:

1. By definition, a quadrilateral is a polygon that has four sides.

2. A rhombus is defined as a quadrilateral, because it has four sides.

Therefore, you can conclude that a quadriletral can be called a rhombus when it has the properties of a rhombus.

Some of hese properties are shown below:

All its sides are equal in length. Its opposite sides are parallel. Its opposite angles are equal. Its diagonals are perpendicular. Its diagonals bisect each other.

when all side of quadrilateral is equal it is called rhombus and none angle is 90.