A set of lines or curves are said to be concurrent if they all intersect. at the same point. In the figure below, the three lines are concurrent because they all intersect at a single point P.

The point P is called the "point of concurrency". This concept appears in the various centers of a triangle. See Centers of a triangle.

Because lines extend indefinitely in both directions, unless they are parallel they will intersect somewhere. Therefore, all non-parallel lines are concurrent. Rays and line segments may, or may not be concurrent, even when not parallel.