Definition:Transversal (Geometry)

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.



Interior Angles
Interior Angles are the angles which are between the two lines cut by a transversal. In the above figure,$$\angle AEF$$, $$\angle CFE$$, $$\angle BEF$$, and $$\angle DFE$$ are interior angles.

Alternate Interior Angles
Alternate interior angles are the angles which are between two lines cut by a transversal, on opposite sides and different lines. In the above figure, $$\angle AEF$$ and $$\angle DFE$$ are a pair of alternate interior angles, as are $$\angle CFE$$ and $$\angle BEF$$.

Corresponding Angles
Corresponding Angles are the angles in equivalent positions on the two lines cut by the transversal with respect to the transversal. For example, $$\angle AEF$$ and the angle from $$C$$ to $$F$$ and then down along $$EF$$ are corresponding angles.