Quadrilateral (noun)

1. A flat shape with four sides and four angles.
2. A polygon with four sides.
3. A figure having four sides, especially a rectangle, a square, a parallelogram, or a trapezium.

Origin:

Late 16th century: from latin quadrilaterus, from quadri- "four" + later "side".

Examples:

1. The quadrilateral was easily transformed into a parallelogram.
2. The area of the quadrilateral was calculated using the formula for a parallelogram.
3. The quadrilateral was used as a base for the pyramid.
4. The quadrilateral was divided into two congruent triangles.
5. The quadrilateral was drawn on the board to demonstrate geometric concepts.