The figure above, the two lines are concurrent because they intersect. (cross) at the point P. For more on this and an animated demonstration see the page defining the concept of intersection.

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.

Points of concurrency

This relates to the centers of triangles. For more see Points of concurrency.

Other line topics

• Point definition
• Line definition
• Line segment
• Midpoint of a line
• Ray
• Opposite rays
• Intersection
• Parallel lines
• Transversal
• Line bisector
• Perpendicular bisector
• Coplanar