A line segment, also known as an interval or closed interval, is 2 connected points. It can be considered as being the solid interior of the 1-dimensional hypersphere, the point pair. A circle can be made by rotating a line segment around the middle axis. People often say a line. A proper line has infinite length. They refer to a line segment when they mean line. A line segment is actually made of an infinite number of points as the line connecting the two points is made up of an infinite number of points.