High Quality Content by WIKIPEDIA articles! In geometry, adjacent angles, often shortened as adj. s, are angles that have a common ray coming out of the vertex going between two other rays. In other words, they are angles that are side by side, or adjacent. A pair of angles are complementary if the sum of their measures is 90°. A pair of angles are supplementary if the sum of their measures is 180°. If the two complementary angles are adjacent (i.e. have a common vertex and share a side, but do not have any interior points in common) their non-shared sides form a right angle.