What does chirality mean?
Chirality is the property of an object or structure that cannot be superimposed on its own mirror image — the way a left hand mirrors but never matches a right hand. Although the idea applies to any asymmetric shape, the word is used most often in chemistry, where many molecules exist as two mirror-image forms known as enantiomers. These forms can behave very differently in biological systems: one may be a life-saving medicine while its mirror twin is inert or even harmful, which is why pharmaceutical scientists pay close attention to molecular chirality. The concept also appears in physics and mathematics, wherever symmetry and handedness matter. Related adjective 'chiral' describes such structures directly. Chirality is a formal scientific term, rarely heard outside academic or technical contexts, yet it captures a fundamental feature of the natural world: that nature itself shows a distinct preference between left and right.
nounThe property of an object or molecule of being distinguishable from its mirror image and not superimposable on it, like a left and right hand.
- In chemistry, physics, and mathematics: the geometric property of a structure that cannot be superimposed on its mirror image.
- By extension, in biology and related fields: the predominance or preference for one handedness over another (e.g., in molecules or organisms).
"The chirality of the drug molecule meant that only one mirror-image form was therapeutically active."
"Amino acids in living organisms display a striking uniformity of chirality, with nearly all occurring in the left-handed form."
"The two enantiomers differ only in their chirality, yet they can smell entirely different to the human nose."
The plural 'chiralities' appears mainly in technical literature when referring to different instances or types of chirality across compounds or contexts.
"The paper surveys the chiralities observed across a range of coordination complexes."
Your hands are mirror images of each other, yet no amount of rotating will make them match — and that everyday fact is exactly what chemists call chirality.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chirality
Chirality derives from the Greek word 'cheir', meaning hand, combined with the suffix '-ality'; it was coined in the late nineteenth century by Lord Kelvin, who used the term in his Baltimore Lectures of 1884 to describe objects not superimposable on their mirror images. The same Greek root gives English several other words relating to hands, including 'chiropractic' and 'chirography' (handwriting), and it underlies 'chiral', the adjectival form of chirality introduced slightly later into chemical usage.
Related word forms
How chirality is actually used
Chirality is a technical term used chiefly in chemistry, physics, mathematics, and biology; it is rare in casual conversation. The corresponding adjective is 'chiral'.
Easily confused with chirality
Handedness refers specifically to the left- or right-handed orientation of a person or object, while chirality is the broader scientific property of being non-superimposable on one's mirror image.