Also called "mirror symmetry", this is a type of
symmetry in which two parts an object are
mirror images of each other. The most common version
of this is
bilateral symmetry, which is (more or less) exhibited by
people and other
vertebrates, as well as
most
insects. Other types of reflection symmetry are possible; for example, images seen in a typical
kaleidoscope will have the sort of symmetry that would be produced by three intersecting
mirrors.
Here are some figures that demonstrate reflection symmetry:
..--====--..
-/ \-
\ /
\ /
/ \
/ \
The first one shows symmetry around only one
plane (a vertical one), but the second shows symmetry around two planes, one vertical and one horizontal.