- a parallelogram in which a diagonal bisects an interior angle
- a parallelogram in which at least two consecutive sides are equal in length
- a parallelogram in which the diagonals are perpendicular (an orthodiagonal parallelogram)
- a quadrilateral with four sides of equal length (by definition)
- a quadrilateral in which the diagonals are perpendicular and bisect each other
- a quadrilateral in which each diagonal bisects two opposite interior angles
- a quadrilateral ABCD possessing a point P in its plane such that the four triangles ABP, BCP, CDP, and DAP are all congruent
- a quadrilateral ABCD in which the incircles in triangles ABC, BCD, CDA and DAB have a common point

## Facts

Area

Equation: