Reflection symmetry

Reflection symmetry, line symmetry, mirror symmetry, mirror-image symmetry, or (in biology) bilateral symmetry is symmetry with respect to reflection. That is, a figure which does not change upon undergoing a reflection has reflectional symmetry.

In 2D there is a line of symmetry, in 3D a plane of symmetry. An object or figure which is indistinguishable from its transformed image is called mirror symmetric.