Final answer:
A quadrilateral with four congruent sides is called a rhombus. It has opposite sides that are parallel, opposite angles that are congruent, and diagonals that bisect each other at 90-degree angles.
Step-by-step explanation:
A quadrilateral with four congruent sides is called a rhombus. A rhombus is a special type of parallelogram where all four sides are equal in length. In addition to having congruent sides, a rhombus also has opposite sides that are parallel, opposite angles that are congruent, and diagonals that bisect each other at 90-degree angles.