What defines an obtuse angle?

An obtuse angle is defined as an angle that measures greater than 90 degrees but less than 180 degrees. This range distinguishes obtuse angles from other types of angles, such as acute angles, which are less than 90 degrees, and straight angles, which measure exactly 180 degrees. The specific criteria of being greater than 90 degrees ensures that the angle opens wider than a right angle but does not extend to a straight line. Thus, identifying an angle within this range allows it to be classified as obtuse, which is a key understanding in geometry when discussing various angle types and their relationships.