What defines an isosceles triangle?

An isosceles triangle is specifically defined as a triangle that has at least two sides of equal length. This equality of sides leads to the two angles opposite those sides being equal as well. Therefore, option C accurately captures this relationship by stating that "two sides and two angles are equal."

In an isosceles triangle, the congruent sides are known as the legs, and the angle formed between these two sides is called the vertex angle, while the other two angles, which are equal, are referred to as the base angles. This property of having two equal sides and two equal angles is fundamental to the classification of isosceles triangles and is crucial in various geometric applications, including proofs and problems involving triangle congruence and similarity.

The other options describe different types of triangles or characteristics that do not pertain to an isosceles triangle. For example, the option that states all sides are equal refers to an equilateral triangle, which is a different category. Similarly, a triangle with no sides equal would be classified as a scalene triangle, while stating that only one angle is right refers to a right triangle, which again does not define an isosceles triangle. The defining feature of an isoscel