What is the term for an angle that measures exactly 90 degrees?

An angle that measures exactly 90 degrees is known as a right angle. This type of angle is significant in geometry, as it is the foundation for creating squares and rectangles, where all angles are right angles. Right angles are often represented by a small square at the corner of the angle, clearly indicating that it measures 90 degrees.

Understanding the characteristics of different types of angles helps in classifying them correctly. An acute angle is one that measures less than 90 degrees, while an obtuse angle measures more than 90 degrees but less than 180 degrees. A reflex angle, on the other hand, measures more than 180 degrees but less than 360 degrees. Therefore, when identifying an angle that is specifically 90 degrees, the term "right angle" is the appropriate choice.