Midpoint of a line segment

See the figure above. The point M is the midpoint of the line segment PQ. Only a line segment can have a midpoint. A line cannot since it goes on indefinitely in both directions, and so has no midpoint. A ray cannot because it has only one end, and hence no midpoint.

When a line cuts another line into two equal parts it is called a bisector. The bisector will cut the line at its midpoint. The midpoint of a line segment can be found using a compass and straightedge. See Constructing the perpendicular bisector of a line segment.

Other line topics

• Point definition
• Line definition
• Vertical lines
• Horizontal lines
• Line segment
• Midpoint of a line
• Ray
• Angle
• Opposite rays
• Intersection
• Parallel lines
• Transversal
• Line bisector
• Perpendicular bisector
• Coplanar
• Collinear points
• Plane