[AntonioLao]

The beginning of an infinitely extended line is at negative infinity if the direction is toward the positive infinity. Therefore, a line always has a starting point and an end point no matter how far they are separated. Any point on the line can be used to describe a preceding point and a succeeding point. On the other hand, a circle could not be simply ordinalized unless a motionless point is marked as the origin. However, continued motion away from the origin along the circumference, whether clockwise or counterclockwise will eventually return to the point of origin. In this sense, the ordinality of the circle is null and that of the line is unity. This unity means there is one and only one direction of motion but there are two degrees of freedom: forward or backward. Forward to positive infinity or backward to negative infinity.