A mirror image of a set 
is the image of 
under reflection in an affine hyperplane.
If the hyperplane is
 |
where 
is a normal vector of unit length, then the mirror
image of a point 
is
 |
The figure above illustrates the case 
, with a point 
and its mirror image 
on opposite sides of the mirror plane 
.
Reflection in a coordinate hyperplane reverses the sign of one coordinate and leaves the others unchanged. More generally, a reflection preserves all distances, so an object and its mirror image are congruent, but it changes handedness. A chiral object cannot be brought into coincidence with its mirror image using only translations and rotations. An object having mirror symmetry, by contrast, agrees with its mirror image for at least one mirror plane.
