A quadrilateral is any four-sided two-dimensional figure. Parallelograms such as squares and rectangles are also quadrilaterals.
No
yes, anything that has four sides is a quadrilateral.
Parallelogram
Any shape that has not got 4 sides is a non-quadrilateral
The formula for the area of a quadrilateral is... BASE*HEIGHT/3
a four sided figure with two 90degree angles on either end of the same line segment. (like a trapezoid)