What defines a square in relation to triangle properties?

A square is defined as a special type of quadrilateral that possesses several distinct properties, one of which is that all its angles measure 90 degrees. This characteristic is essential because it contributes to the square being both a rectangle (where opposite angles are equal and all angles are right angles) and a rhombus (where all sides are equal, making the opposite angles equal).

The fact that all angles in a square are right angles ensures that the square has the necessary structure to be classified as a highly symmetrical shape, which is integral in various mathematical applications and proofs. Understanding this aspect helps in visualizing and distinguishing squares from other quadrilaterals, such as rectangles and parallelograms, where the angle conditions differ.

While the other options present different characteristics that may apply to shapes in geometry, they do not correctly describe a fundamental property of a square. For example, having only two equal sides is indicative of an isosceles triangle rather than a square. Therefore, recognizing that a square has all angles measuring 90 degrees is key in geometry, particularly when understanding properties of polygons and their significance in both two-dimensional and three-dimensional spaces.