Final answer:
A rhombus is the quadrilateral in which all four sides are congruent, distinguishing it from parallelograms, rectangles, and trapezoids which do not necessarily have all sides of equal length.
Step-by-step explanation:
All four sides are congruent in a rhombus. A rhombus is a special type of parallelogram where all sides have equal length. It is important to note that while all sides of a rhombus are congruent, this characteristic is not true for all parallelograms, rectangles, or trapezoids. For instance, a rectangle has opposite sides that are equal, but not necessarily all four sides. A trapezoid generally has only one pair of parallel sides and the side lengths can vary. In the case of a parallelogram, opposite sides are equal and parallel but adjacent sides can be of different lengths, except when it is a rhombus where all sides are equal.