Chemistry Chirality is the property of a three-dimensional object of being non-superposable on its mirror image.
The etymology of the word refers to the fact that the right and left hands, though images of each other in a plane of symmetry, are not superposable.
A molecule is chiral if it has no plane of symmetry (a necessary and sufficient condition). The presence of an asymmetric carbon in a compound is a sufficient but not a necessary condition for it to be chiral.
This asymmetry is at the origin of the optical activity of chiral molecules. Two chiral molecules that are images of each other are called enantiomers and have the same physical properties except that their specific rotations are opposite. They have the same chemical properties except for chemical reactions involving the chiral centre.
Most natural molecules are chiral, with one form or the other predominating, such as the L form of the amino acids. This is why we speak of the handedness of nature, the origin of which remains unknown.