When can a rhombus also be called a square?

When a rhombus has four equal angles that measure 90°, it can be called "a square".

Step-by-step explanation:

It is important to remember that, by definition, a Quadrilateral is a polygon that has four sides.

A rhombus is a quadrilateral because it has four sides. Some properties of a rhombus are:

- All its sides are equal in length.

- Its opposite sides are parallel.

- Its opposite angles are equal.

A square is also a quadrilateral, because it has four sides.

These are some of its properties:

- All its sides have equal lenght.

- Its opposite sides are parallel.

- All its angles measures 90° (also known as "right angles")

Based on this, we can conclude that a square is a rhombus.

Therefore, when a rhombus has four equal angles that measure 90°, it can be called "a square".