Definition 3
The ends of a line are points.
This statement can be taken as indicating that between certain lines and points a relation holds, that a point can be an end of a line. It doesn't say what ends are. It also doesn't indicate how many ends a line can have. For instance, the circumference of a circle has no ends, but a finite line has its two end points.
Book I Introduction -
Definition 2 -
Definition 4.
© 1996
D.E.Joyce
Clark University