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 specific angle is significant in geometry and serves as the foundation for various concepts, such as defining perpendicular lines, which intersect to form right angles. Visualizing a square corner, where two straight lines meet at a perfect angle to form a "quarter turn," can help in understanding this concept.

In contrast, acute angles are those measuring less than 90 degrees, while obtuse angles measure more than 90 degrees but less than 180 degrees. A straight angle, on the other hand, measures exactly 180 degrees, representing a straight line. Recognizing the characteristics of these different angles is crucial for understanding basic geometric principles and their applications in various mathematical contexts.