A rectangular section can be obtained by oblique cutting parallel to one side. Cut a cube with a plane, and the cross section will be triangular, quadrilateral and hexagonal. If a pentagon is cut into a quadrilateral, it must be a parallelogram.

The distance between parallel lines is the distance from any point on a straight line to another point, which is called the distance between two parallel lines. According to the definition of parallel distance, every two distances and two parallel lines form a parallelogram, so there are countless parallelograms. According to the characteristics of parallelogram, the distance between parallel lines is equal everywhere.

Other attributes

The opposite sides of a parallelogram are parallel (by definition), so they will never intersect.

The area of a parallelogram is twice the area of a triangle formed by one of its diagonals.

The area of parallelogram is also equal to the cross product of two adjacent edge vectors.

Any line passing through the midpoint of the parallelogram divides the area in two.

Any nondegenerate affine transformation adopts parallelogram.