Points, Lines, and Rays

2.1 Point

A point determines a precise location. It has no length, breadth, or height. We usually represent it with a dot and name it using a single capital letter.

• Models: The tip of a compass, the sharpened end of a pencil, the pointed end of a needle.
• Notation: Point $P$, Point $Z$.

2.2 Line Segment

If you mark two points, A and B, on a paper, the shortest route connecting them is the line segment from A to B.

• End Points: It has two fixed end points, $A$ and $B$.
• Notation: $\overline{AB}$ or $\overline{BA}$.
• Length: It has a definite length that can be measured.

2.3 Line

Imagine extending a line segment $\overline{AB}$ endlessly in both directions. This forms a line.

• Properties: It has no end points and extends forever. It cannot be drawn completely on paper, so we use arrows at the ends to show it continues.
• Notation: $\overleftrightarrow{AB}$ or a small letter like $l$, $m$.

2.4 Ray

A ray is a portion of a line that starts at one point (called the starting or initial point) and goes on endlessly in one direction.

• Models: Beam of light from a lighthouse, sun rays, light from a torch.
• Notation: $\overrightarrow{AP}$. Here, $A$ is the starting point, and it passes through $P$.