What defines an acute triangle?

An acute triangle is defined specifically by the property that all of its interior angles are less than 90 degrees. This characteristic distinguishes acute triangles from other types of triangles, such as right triangles, which have one angle equal to 90 degrees, and obtuse triangles, where one angle exceeds 90 degrees.

In acute triangles, since all angles are acute, this leads to unique properties such as the sum of the angles still being 180 degrees while maintaining the criteria for each angle being under 90 degrees. This definition makes it clear that option B accurately captures the essence of what constitutes an acute triangle. Understanding this definition is essential in the study of triangles, as it sets a foundation for recognizing and differentiating between various triangle types in geometry.