Chirality
Chirality /kaɪˈrælɪtiː/ is a property of asymmetry important in several branches of science. The word
chirality is derived from the Greek,
χειρ, "hand", a familiar chiral object. An object or a system is
chiral if it is not identical to its mirror image, that is, it cannot be superposed onto it. A chiral object and its mirror image are called
enantiomorphs or, when referring to molecules,
enantiomers. A non-chiral object is called
achiral and can be superposed on its mirror image. The term was first used by Lord Kelvin in 1893 in the second Robert Boyle Lecture at the Oxford University Junior Scientific Club which was published in 1894.
I call any geometrical figure, or group of points, 'chiral', and say that it has chirality if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself. Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superimposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide.