Adjacent angle

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In the illustration, angles A and B are adjacent.

In geometry, adjacent angles are angles that have a common ray coming out of the vertex going between two other rays.

[edit] Supplementary adjacent angles

A pair of angles is supplementary if their measurements add up to 180 degrees. If the two supplementary 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 straight line

[edit] Complementary adjacent angles

A pair of angles are complementary if the sum of their angles is 90°.

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.

In Euclidean geometry, the two acute angles in a right triangle are complementary, because there are 180° in a triangle and 90° have been accounted for by the right angle. These angles would be adjacent. on 120 degrees