In
geometry, a figure is
chiral (and said to have
chirality) if it is not identical to its
mirror image, or, more precisely, if it cannot be mapped to its mirror image by
rotations and
translations alone. An object that is not chiral is said to be achiral. In 3 dimensions, not all achiral objects have a mirror plane. For example, a 3-dimensional object with
inversion centre as its only nontrivial
symmetry operation is achiral but has no mirror plane.