# Straight Line

The locus of oppositely and infinitely travelling two points from a position on a plane is called a straight line.

Straight line is a basic geometrical concept and it plays vital role in studying the geometry. It has length but infinite and it does not have width, thickness and curvature.

### Formation

1. $P$ and $Q$ are two points on a plane and they are at same location initially.
2. The point $P$ is started travelling in left side direction from its initial position and continues travelling infinitely in the same direction. Simultaneously, the point $Q$ is also started travelling in right side direction from its initial position and continues travelling infinitely in the same direction.
3. The locus of these two infinitely and oppositely travelling points form a straight path and it is called straight line.

#### Representation

A straight line is represented in mathematics based on its geometrical formation.

1. Write the names of two points which involve in forming a straight line but name of left point first and then name of right point next.
2. Display a Left-Right arrow $(\longleftrightarrow)$ symbol over the names of both the points to represent oppositely and infinitely extended path symbolically.

Here, the points $P$ and $Q$ formed a straight line. So, the points $P$ and $Q$ are written as $PQ$ firstly and then draw left-right arrow over the $PQ$. It means $\overleftrightarrow{PQ}$ is the symbolic representation of a line in mathematics.

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