Parallelogram with equal diagonal lines

A quadrilateral with three internal angles at right angles.

A quadrilateral with equal diagonals and bisecting each other.

A rectangle must have one set of opposite sides parallel to the X axis and another set of opposite sides parallel to the Y axis. Geometric rectangles that do not meet this condition are regarded as general quadrilaterals in computer graphics. In advanced mathematics, only the rectangle is mentioned, so the length and width of the rectangle are not mentioned.