Hyperparallel

Two hyperparallel lines have one and only one common perpendicular.

Let l and m be two hyperparallel lines. All the transversals to l and m that form congruent corresponding angles with l and m lie in a pencil.

In order that two distinct lines K and L be hyperparallel it is necessary and sufficient that they lie in one plane and that there exists a line M intersecting both of them perpendicularly.