reflection

In geometry, a transformation that reflects every point on a shape to a point that is the same distance on the opposite side of a fixed line - the mirror line, or line of symmetry. Reflections in two perpendicular axes produce a rotation of 180° (a half turn).

For example, in the following diagram, triangle A has been reflected along the y-axis (the mirror line) to obtain triangle B:

If triangle B is reflected again along the mirror line to triangle A, the movement would be an inverse transformation. Shapes can also be transformed by translation, rotation, and enlargement.