Lines: Intersecting, Perpendicular, Parallel

You have probably had the experience of standing in line for a movie ticket, a bus ride, or something for which the demand was so great it was necessary to wait your turn. However, in geometry, there are three types of lines that students should understand.

Intersecting lines


Two or more lines that meet at a point are called intersecting lines. That point would be on each of these lines. In Figure 1, lines l and m intersect at Q.



Figure 1 Intersecting lines



Perpendicular lines


Two lines that intersect and form right angles are called perpendicular lines. The symbol ⊥ is used to denote perpendicular lines. In Figure , line l ⊥ line m.





Figure 2 Perpendicular lines.


Parallel lines

Two lines, both in the same plane, that never intersect are called parallel lines. Parallel lines remain the same distance apart at all times. The symbol // is used to denote parallel lines. In Figure 3, l // m.





Figure 3 Parallel lines.