There are four types of lines: horizontal line, vertical line, perpendicular, and parallel lines. They are defined based on their orientation, and the angles if any, formed between them. Let’s look at each one of them.
A line has no beginning point or end point. Imagine it continuing indefinitely to both directions. We can illustrate that by little arrows on both ends.
A line segment has a beginning point and an end point.
A ray has a beginning point but no end point. Think of sun's rays: they start at sun and go on forever...
Horizontal line
A line that runs from left to right in a straight line is called a horizontal line.
Vertical line
A line that runs from top to bottom in a straight line is a vertical line.
Perpendicular
When two straight lines intersect (i.e.cross) each other at right angles (= 90°), then these two lines are said to be perpendicular to each other.
Here AB and CD are the two perpendicular lines, and they are represented as .
Parallel lines
When two lines never meet each other, no matter how much you extend them, then these two lines are said to be parallel to each other.
Lines AB and CD are parallel lines, and are always the same distance apart from each other. Parallel lines are represented by the two large arrows on the lines, and are represented as