A line is a group of points on
a straight path that extends to infinity.

Any two points on the line can be used
to name it. This line is called line DE.

A line segment is a part of a line that has
two end points.

The two end points of the line segment
are used to name the line segment. This line segment is called
segment XY.

A ray is part of a line.
It has one end point and extends to infinity in one direction.
A ray is named starting with its end point first and then any
other point on the ray second.

Using the graphic to the
left: Name a line:
Name a line segment with U as an
end point: Name a ray with V as
an end point: