Definition:Transversal (Geometry)/Alternate Angles

Definition

 * Alternate Interior Angles.png

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, the pairs of alternate interior angles with respect to the transversal $EF$ are:
 * $\angle AHJ$ and $\angle DJH$
 * $\angle CJH$ and $\angle BHJ$

Also see

 * Equal Alternate Interior Angles implies Parallel Lines
 * Parallelism implies Equal Alternate Interior Angles