Quadrilaterals are closed, co-planar geometric shapes that comprise two diagonals and four sides, where all four interior angles have a sum of 360 degrees. Special types of quadrilaterals include parallelograms, rectangles, squares, rhombuses, trapezoids and kites.
Parallelograms contain two pairs of opposing sides that are parallel and equally long. The opposite angles of parallelograms are also equal. Rectangles, squares and rhombuses are considered parallelograms because they share the same properties as a parallelogram.
The four interior angles of rectangles and squares are all right angles, or 90-degree angles. The opposite angles, also called supplementary angles, have a sum of 180 degrees.Learn more about Geometry