Ray
The locus of a point in a direction from a position in a plane is called a ray.
A ray is a one directional straight line. It is actually formed by a point which starts from a position on a plane and continues its traveling infinitely in a direction. It seems, it is half of the straight line.
Formation

- $\small R$ is a location in a plane.
- A point is started travelling from location $\small R$ and continued travelling infinitely in the same direction by passing through various points including $\small S$.
- The locus of the travelling point from a location in a particular direction formed a straight path and it is called a ray.
Representation
A special mathematical representation is used to denote a ray in mathematics and it is developed as per the geometric formation of the ray.
- Write the names of two points one after one but the name of the first point should be the point where the straight path is started.
- Display a right arrow symbol $(\rightarrow)$ over the names of both points which play a vital role in forming the ray.
In this example, $R$ is a starting point $S$ is any point on the straight path. Write the names of them as $RS$ and display a right arrow symbol over names of both points.
Therefore, $\overrightarrow{RS}$ is the mathematical representation of a ray. Thus, any ray can be denoted mathematically in this manner.
