Definition:Transversal (Geometry)

Definition
A transversal of two lines lying in the same plane is a line which intersects them in two different points.

The transversal is said to cut the two lines that it crosses.


 * Transversal.png

In the above diagram, $EF$ is a transversal of the lines $AB$ and $CD$.

It is also apparent that:
 * $AB$ is a transversal of the lines $EF$ and $CD$
 * $CD$ is a transversal of the lines $EF$ and $AB$

although this is not as obvious.

Also see

 * Equal Alternate Angles implies Parallel Lines
 * Equal Corresponding Angles or Supplementary Interior Angles implies Parallel Lines
 * Parallelism implies Equal Alternate Angles, Corresponding Angles, and Supplementary Interior Angles