Points, lines and segments

Lines, line segments, and rays

Line:
A line is a set of continuous points that extend indefinitely in either direction.
A line is identified by naming two points on the line and drawing a line over the letters . Alternatively, a line may be named by using a single lowercase letter (line l).

Line segment:
A line segment is a part of a line consisting of two points, called end points, and the set of all points between them.
A line segment is identified by naming the two end points and drawing a line over the letters
.

It is crucial to understand how to define and correctly label line segments because they form the sides of polygons and appear in countless ways.

Ray:
A ray is a part of a line consisting of a given point, called the end point, and the set of all points on one side of the end point.
A ray is always named by using two points, the first of which must be the end point. The arrow drawn above always points to the right:

What is this?

line
line segment
ray