What type of angle is defined as being exactly 180 degrees?

An angle that measures exactly 180 degrees is known as a straight angle. This type of angle is formed when the two rays (or sides) of the angle are oriented in exactly opposite directions, creating a straight line.

In geometric terms, the key characteristic of a straight angle is that it divides a straight line into two equal parts, leading to its representation as a flat angle. Understanding this definition is critical as it differentiates straight angles from other types of angles. For example, acute angles measure less than 90 degrees, obtuse angles range between 90 and 180 degrees, and reflex angles measure more than 180 degrees but less than 360 degrees. Therefore, the distinct measurement of 180 degrees uniquely qualifies this angle as a straight angle.