When these quadrilaterals are   not convex, they can be called darts or arrowheads.
This is the most general quadrilateral for which exactly one pair of opposite vertices are equidistant   from any fixed point on the diagonal that does not go through them. Like rhombuses and squares,  these quadrilaterals have inscribed circles and perpendicular diagonals. When these quadrilaterals are   not convex, they can be called darts or arrowheads. One of this shape's diagonals is the perpendicular  bisector of the other, which is useful when proving that these shapes have one pair of congruent  angles. Name these shapes, also called deltoids, that have two pairs of congruent adjacent sides.
This is the most general quadrilateral for which exactly one pair of opposite vertices are equidistant   from any fixed point on the diagonal that does not go through them.
kites [prompt on deltoids]