Question

A parallelogram with four equal sides is also called a _______?

Answer 1

A parallelogram with `4` equal sides is a rhombus.

Explanation:

A rhombus is: "A quadrilateral with both pairs of opposite sides parallel and all sides the same length, i.e., an equilateral parallelogram."
(cite from: http://mathworld.wolfram.com/Rhombus.html)

In previous answer square was mentioned, but it is not correct, because a square must also have 4 right angles which is not a condition for a rhombus.