The defining property of complementary angles is that their measures add up to 90°.Since each angle in a complementary pair must be less than 90° to satisfy the sum requirement, both angles are always acute.

The defining characteristic of supplementary angles is that their measures add up to 180°. Since the sum is 180°, one of the angles can be obtuse (greater than 90°) while the other is acute (less than 90°). Alternatively, both angles can be right angles (90° each).