case is a trilateral trapezoid or a trisosceles trapezoid, where two legs and one base have equal lengths; it can be considered as the dissection of a regular hexagon.

Any non-self-crossing quadrilateral with exactly one axis of symmetry must be either an isosceles trapezoid or a kite. However, if crossings are allowed, the set of symmetric quadrilaterals must be expanded to include also the crossed isosceles trapezoids