A kite.
Because the diagonals in a square are at right angles to one another!
It is a rhombus whose diagonals are perpendicular and meeting each other at right angles.
Square, rhombus and a kite quadrilateral
A kite.
A Quadrilateral Kite!
If you are not a square then you are a rectangle.
rhombus
kkk
Two pairs of touching sides are the same length. The diagonals meet at right angles. Opposite sides are not parallel.
A trapezoid Trapezoid - 2 congruent diagonals that do not bisect each other. No right angles and has 1 pair of opposite parallel sides.
A rectangle.
Four straight sides, four right angels, diagonals that bisect one another.