What defines congruent triangles?

Congruent triangles are defined as triangles that have the same shape and size. This means that when one triangle is superimposed over another, they match perfectly in terms of both dimensions and angles. This fundamental definition establishes that all corresponding sides and angles of these triangles are equal, leading to the conclusion that if two triangles are congruent, they can be considered identical in these respects.

The other options highlight important characteristics of triangles, but they do not fully encapsulate the definition of congruence. For instance, triangles with the same angles may not have the same sizes, which means they could be similar but not congruent. Similarly, equal perimeter does not guarantee that two triangles are congruent, as they might have different configurations or side lengths while still totaling the same perimeter. The claim that all triangles are congruent is inherently inaccurate, as there are clearly many different shapes and sizes of triangles. Thus, the only correct and complete definition of congruent triangles is that they have the same shape and size.