diameter
A line segment is a portion of a line. It has length. It has two endpoints. A ray has only one endpoint. It has infinite length in one direction.
A ray = A half-line
a ray
Not necessarily - it depends on the geometry. The equator, on a sphere like the earth, is a straight line on a spherical surface. It has no endpoint.
The line segment is a radius.
The segment you describe is the radius of the circle.
diameter
radius
By definition a line has no endpoint as it can extend to negative and positive infinity. A ray has one endpoint and a segment has two endpoints.
Such a line segment would be a radius of the circle.
A ray,------------------->
segment
A radius.
A line segment has two endpoints
In geometry, a line has no endpoints. If it has one endpoint and continues infinitely, it is a ray. If it has two endpoints, it is a line segment. If it has one end that approaches but never reaches a point, it is a half line.
A ray has one point and one that goes on forever, a line segment has two points.