Why consecutive angles are supplementary?

Consecutive angles, also known as adjacent angles, are supplementary when they are formed by two intersecting lines or when they share a common side. This means that the angles add up to 180 degrees. In the case of a linear pair, the two angles are directly next to each other on a straight line, thus ensuring their measures sum to a straight angle of 180 degrees. This property is fundamental in geometry and is used in various proofs and applications.