The operation of exchanging all points of a mathematical object with their mirror images (i.e., reflections in a mirror). Objects that do not change handedness
under reflection are said to be amphichiral; those
that do are said to be chiral.

Consider the geometry of the left figure in which a point is reflected in a mirror (blue line). Then

(1)

so the reflection of
is given by

(2)

The term reflection can also refer to the reflection of a ball, ray of light, etc. off a flat surface. As shown in the right diagram above, the reflection of
a points
off a wall with normal vector satisfies

(3)

If the plane of reflection is taken as the -plane, the reflection in two- or
three-dimensional space consists of making the transformation
for each point. Consider an arbitrary
point and a plane
specified by the equation