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Definition 3

The ends of a line are points.

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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