A ray is a portion of a line. It starts at one point (called starting
point) and goes endlessly in a direction.
Examples of the ray are: Beam of light from a lighthouse and sun rays.
Thus a line segment extended endlessly in the direction from
A to B, is a ray denoted by
The ray has one end (fixed) point called its initial point.
Rays and are two different rays.
Ray is a ray with initial point B and extends endlessly in the
direction from B to A.