Segment
the part of a line consisting of two end points and all points between them.
Ray
Part of a line consisting of one endpoint and all the points of a line on one side of the endpoint
Opposite Rays
Two collinear rays with the same endpoint.
Parallel lines
Coplanar lines that do not intersect
Skew lines
noncoplanar therefore they are not parallel and do not intersect
Parallel lines
planes that do not intersect