What does chiral mean?
Chiral describes an object or molecule that cannot be superimposed on its mirror image — much like a left and right hand, which are mirror reflections yet can never be made to match up exactly, palm for palm. The word derives from the Greek 'cheir,' meaning hand, and entered English through nineteenth-century science. In chemistry, chirality is a property of profound importance: many molecules exist as two mirror-image forms, called enantiomers, which can behave dramatically differently in biological systems. Famously, one form of the drug thalidomide was therapeutic while its mirror image caused severe birth defects, making chirality a central concern in pharmaceutical design. Beyond chemistry, mathematicians and physicists use 'chiral' to describe anything with inherent handedness, from spirals to subatomic particles. Though chiefly a scientific term, it offers a vivid way to describe asymmetry and mirror-image distinction in any context.
adjectiveHaving a structure that is not superimposable on its mirror image; in chemistry, describing a molecule that exists in two mirror-image forms (enantiomers). More generally, relating to or exhibiting handedness.
- (Chemistry) Of a molecule: having a structure not superimposable on its mirror image, typically due to an asymmetric carbon atom.
- (General/physics & mathematics) Exhibiting handedness; distinguishable from its mirror image.
"The drug's two chiral forms have very different effects on the body."
"Amino acids in living organisms are almost exclusively found in their left-handed chiral form."
"The crystal exhibits a chiral structure that rotates polarized light."
Your hands are the reason the word exists: 'chiral' comes from the Greek for hand, because hands are mirror images that can never be perfectly stacked on each other.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chiral
The adjective 'chiral' derives from the ancient Greek word 'cheir' (χείρ), meaning hand, via the combining form 'chir-.' It was coined in the late nineteenth century by Lord Kelvin, who introduced the concept of 'chirality' in an 1884 lecture to describe objects distinguished from their mirror images. The same Greek root gives us 'chiropractic,' 'chiromancy' (palm reading), and, more distantly through Latin 'chirurgia,' the words 'surgery' and 'surgeon.'
Related word forms
How chiral is actually used
Primarily a technical term used in chemistry, physics, and mathematics; rarely heard in everyday conversation. It carries no emotional connotation and is neutral in register, though it signals scientific literacy when used correctly.
Easily confused with chiral
'Choral' relates to a choir or singing by a group, while 'chiral' describes objects or molecules with handedness — they look similar but are unrelated.