What characterizes a right triangle?

A right triangle is characterized by having one right angle, which measures exactly 90 degrees. This defining feature sets right triangles apart from other types of triangles. In contrast, a triangle labeled as having all acute angles (where each angle is less than 90 degrees) would be classified as an acute triangle. The option that mentions having two equal sides describes an isosceles triangle, which can be either a right triangle or an acute triangle, but does not define a right triangle on its own. Lastly, the description of having no right angles would identify an obtuse or acute triangle but not a right triangle. Thus, the presence of one right angle is essential to the classification of a triangle as a right triangle.