quadrilateral
polygon with four sides
cyclic quadrilateral
quadrilateral whose vertices can all fall on a single circle
rhombus
quadrilateral in which all sides have the same length
trapezoid
convex quadrilateral with at least one pair of parallel sides
general irregular quadrilateral
quadrilateral with no parallel sides
rectangle
quadrilateral with four right angles
harmonic quadrilateral
cyclic quadrangle in which the products of the lengths of opposite sides are equal
skew quadrilateral
skew polygon with four side
Trapezium
Wikimedia disambiguation page
Lambert quadrilateral
quadrilateral with three right angles
complete quadrangle
four points that determine six distinct lines