Line Segment, Ray, and Line

Three related but different objects

• A line segment has two endpoints and a fixed, definite length.
• A ray has one endpoint and extends infinitely in a single direction, so it has no definite length.
• A line has no endpoints at all: it extends infinitely in both directions, so a complete line can only be represented on paper (with arrowheads showing it continues), not fully drawn.

Collinear points and concurrent lines

Three or more points that all lie on the same line are called collinear. Three or more lines that all pass through the same single point are called concurrent.

Quick true/false check

"A ray has no end point.": False. A ray has exactly one endpoint (where it starts); it's only unbounded on the other end.

"A line can be drawn on paper.": False, strictly speaking: since a line is infinite in both directions, what actually gets drawn is only a segment that represents the line.