Shapes that don't have 4 sides are not quadrilaterals
quadrilateral - quad means four A quadrilateral has four sides
A quadrilateral has four sides. A circle does not have four sides. Therefore, a circle is not a quadrilateral.
2 opposite acute angles and 2 opposite obtuse angles with opposite parallel sides
A quardrilateral with 1 pair of parallel lines and have no equal sides is a trapezium.
Hexagon means 6-sided (from greek) Quadrilater means 4-sided (from latin)
This can be a square or a rectangle.