Angles whose measures add up to 90°.
Two complementary adjacent angles form a right angle.
Examples
In this figure, angles A and B are complementary, since the sum of their measures is 90°.
Since these angles are adjacent, they form a right angle.
In the figure below, where a pair of parallel lines intersects another pair of parallel lines, angles A and B are also complementary, even though they are not adjacent. In fact, a translation can be applied to make the vertices of angle A and angle B coincide and form a right angle.
