Line segment, Line and Ray

1.                        Line segment

A line segment is a part of a line, which has two end points, and  contain all of the points between the two end points.

In a sheet of a paper draw two points A and B, and joint the A and B (including A and B) to shortest route that is the line segment AB.
                                         __     __
                 It is denoted by AB or BA .

The points A and B are called the end points of the segments.

                                                                                                            A ______________________B

2.                               Line

A line is straight (no curves), has no thickness, and extends indefinitely in both directions.
It contains countless numbers of points.
Two points are enough to fix a line.                                     ↔

The line AB is written as AB.

3.                               Ray

A ray is a portion of a line. It starts at one point called starting point and extends infinity in one direction.                                     

→
The ray AB is written as AB.