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__Ray__

**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 **i**s a ray with initial point B and extends endlessly in the
direction from B to A.**