A kite is a planar convex quadrilateral consisting of two adjacent sides of length a and the other two sides of length b that are congruent. It is notable that the diagonals of a kite are perpendicular. The rhombus is a special case of the kite, and the lozenge is a special case of the rhombus. Below is an example of a kite.
The area of a kite is given by A = 1⁄2 pq, where p = √ a2 - h2 + √ b2 - h2 and q = 2h are the lengths of the polygon diagonals (which are perpendicular). The 120-90-60-90 kite with edge ratios √ 3 : 1 is the basis for the polyomino-like objects known as polykites.
“Kite.” From Wolfram MathWorld, mathworld.wolfram.com/Kite.html.