The term for the angle in a triangle that measures less than 90 degrees is "acute angle." In a triangle, an acute angle can be part of any triangle type, including acute triangles, where all angles are acute. Acute angles are characterized by their sharpness, as they measure between 0 and 90 degrees. Understanding acute angles is fundamental in geometry, where they play a significant role in various calculations involving triangles, such as determining area and applying the Pythagorean theorem. The concept of acute angles also extends beyond triangles, appearing in various mathematical and real-life contexts.