What is the definition of a parallellogram?

A parallelogram is a four-sided polygon (quadrilateral) with opposite sides that are both equal in length and parallel. Additionally, the opposite angles in a parallelogram are equal, and the consecutive angles are supplementary. Common examples of parallelograms include rectangles, rhombuses, and squares. The area of a parallelogram can be calculated using the formula ( \text{Area} = \text{base} \times \text{height} ).