Chirality

Chirality () is the property of an object not being identical to its reflection, or mirror image. An object is chiral if it is not identical to its reflection; that is, it cannot be superposed (mapped by rotations and translations alone) onto itself. Conversely, an object is achiral (sometimes also amphichiral) if its reflection cannot be distinguished from the object (i.e. can be superposed onto its reflection), such as a sphere. A chiral object and its reflection are called enantiomorphs (from Greek for 'opposite forms') or, when referring to molecules, enantiomers. Chirality is a property of asymmetry important in several branches of science. Human hands are perhaps the most recognized example of chirality. The left hand is a non-superposable 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 across all axes. This difference in symmetry becomes obvious if someone attempts to shake the right hand of a person using their left hand, or if a left-handed glove is placed on a right hand. The word chirality is derived from the Ancient Greek χείρ (kheír), meaning 'hand', a familiar chiral object. 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.