The animation above shows one way to think of the definition of a
line segment, as an infinite number of points.
Parts of lines are called line segments
segments. They are made up of two points on a line and all the
points on the line between them. The two points are called endpoints and are named by
capital letters, just like other points. A line segment can also be named by a symbol
like, where A and B are the endpoints of the segment.