Two lines in a plane can either be parallel or intersecting. Three lines in a plane may:

- be parallel to each other, i.e., intersect in no point
- intersect each other in exactly one point
- intersect each other in two points
- intersect each other at the most in three points

Three lines in a plane which intersect each other in exactly one point or which pass through the same point are called **concurrent lines** and the common point is called the **point of concurrency**.