Line segment (Interval)
If A and B are two points on a line, the part of the line between and including A and B is called a line segment or interval.
The distance AB is a measure of the size or length of AB.
Any point A on a line divides the line into two pieces called rays. The ray AP is that ray which contains the point P (and the point A). The point A is called the vertex of the ray and it lies on the ray.