Which angle is defined by an exact measurement of 90 degrees?

A right angle is defined as an angle that measures exactly 90 degrees. This is a fundamental concept in geometry, as it represents a quarter turn or the angle formed when two lines are perpendicular to each other. Right angles are critical in various applications, such as construction and design, where the integrity of structures relies on precise angles. Understanding the properties of angles, including that a right angle has this exact measurement, is essential for students as they progress in their mathematical education and practical applications.