The tetrahedron, for example, has 120-degree rotational symmetry around the axes going from any vertex to the opposite face. It also has reflective symmetry across each plane that goes through an ...

But symmetry is more generally defined as immunity to a possible change. For example, the phrase “Madam I’m Adam” reads the same if read back-to-front letter by letter.

For example, to completely specify a perfect square, which is symmetric under rotation by 90 degrees about an axis perpendicular to its area through its center; and also symmetric under reflection ...