Which concept describes an invariant property under reflection or rotation?

• A. Invariance
• B. Symmetry
• C. Congruence
• D. Equivalence

Answer: (B)

Symmetry is when a figure looks the same after applying a reflection or a rotation. This means the property is unchanged under those transformations. For example, a circle has rotational and reflection symmetry: rotating it by any angle or reflecting across any line through the center leaves it unchanged. A square also has symmetry under 90-degree rotations and under reflections across its axes and diagonals. In this sense, symmetry is the specific term that captures invariant behavior under those geometric transformations, whereas invariance is a broader idea, congruence is about two shapes being the same size and shape, and equivalence is a relational notion not tied to these geometric transformations.