Final answer:
When two parallel lines are intersected by a transversal, 4 pairs of alternate interior angles are formed. These angles are on opposite sides of the transversal and inside the parallel lines.
Step-by-step explanation:
When two parallel lines are intersected by a transversal, 4 pairs of alternate interior angles are formed. These angles are called 'alternate' because they are on opposite sides of the transversal, and 'interior' because they are inside the parallel lines. For example, if we have parallel lines AB and CD intersected by transversal EF at points G and H, angles BGC and HDG would be one pair of alternate interior angles, and angles CGH and BGH would be another pair. Similarly, on the other side, angles AGF and DHF, FHD and FHE would make up the other two pairs.
Learn more about Parallel Lines and Transversals