Which type of triangle has at least two congruent sides?

An isosceles triangle is defined as having at least two sides that are congruent, meaning they are of equal length. This attribute distinguishes it from other types of triangles. In the context of triangle classification, an isosceles triangle will also have angles opposite the congruent sides that are equal, which reinforces the significance of its symmetry.

While an equilateral triangle also has congruent sides, having all three sides equal, the definition of an isosceles triangle is broader since it encompasses any triangle with at least two equal sides, regardless of the third side's length. This makes isosceles triangles more versatile in terms of classification.

In contrast, a scalene triangle is characterized by having all sides of different lengths, and an acute triangle is defined based on its angles, with all angles measuring less than 90 degrees. Thus, the isosceles triangle stands out specifically for its unique property of having two sides that are the same length.