What is called a ray? What is called a segment?

A ray is a part of a line that starts at a point and goes out in a certain direction to infinity. On the way to infinity, he can pass through one or more other points. The ray is one-dimensional. It is zero-width. If you draw a beam with a pencil, examination with a microscope will show that the pencil mark has a measurable width. The ray has no measurable length because it continues forever in one direction.

A segment is a connected part of a real line. If the end points A and B are end points and are included, then the segment is called closed and denoted by [A, B]. If endpoints are not included, the line is said to be open and denoted (A, b). If one endpoint is on, but not the other, the line is denoted by [A, B) or (A, B] and is called a semi-closed (or half-open) line.