What type of angle measures less than 90 degrees?

An acute angle is defined as an angle that measures less than 90 degrees. This characteristic distinguishes acute angles from other types of angles. For example, an obtuse angle measures more than 90 degrees but less than 180 degrees, which is the opposite of what is required in this case. A right angle, on the other hand, is exactly 90 degrees, so it does not fall under the criterion of being less than 90 degrees. Supplementary angles refer to two angles that add up to 180 degrees, which also does not match the definition of measuring less than 90 degrees. Therefore, the identification of an acute angle as the type of angle that measures less than 90 degrees is correct, as it fits the criteria perfectly.