Chirality is a property of asymmetry important in several branches of science. The word chirality is derived from the "hand," a familiar chiral object. An object or a system is chiral if it is distinguishable from its mirror image; that is, it cannot be superimposed onto it.
Chiral molecules are always dissymmetric (lacking Sn) but not always asymmetric (lacking all symmetry elements except the trivial identity). Asymmetric molecules are always chiral. Molecular symmetry and chirality
A molecule has the property of chirality (dissymmetry) when its mirror image is non-superimposable on itself. The non-superimposable mirror image isomers are called enantiomers, but also may be referred to as enantiomorphs, optical isomers, or optical antipodes.