What does helicity mean?
Helicity is a technical noun describing the twisting associated with a helix, or spiral structure. Its most familiar use is in molecular biology and biophysics, where the helicity of DNA or RNA refers to the degree and handedness of its helical winding. These structural properties are important because they affect how nucleic acids interact with proteins and whether they can carry out their normal functions. Helicity also has a specialized meaning in particle physics: it describes the projection of a particle’s angular momentum along its direction of motion and helps distinguish right-handed from left-handed states. Related uses occur in knot theory and fluid mechanics, where the term describes linking or twisting. Although the word may sound familiar because of the common name “double helix,” helicity is not everyday vocabulary. It is most useful when precision is needed about the form, orientation, or twisting of a helical system.
nounHelicity is the degree of twisting associated with a helical structure, especially the twisting of DNA or RNA. In particle physics, it also refers to the component of a particle's angular momentum projected along its direction of motion.
- In molecular biology and biophysics, the degree to which a nucleic acid or other molecular chain is twisted into a helix.
- In particle physics, the quantum number associated with the projection of angular momentum onto a particle's direction of motion, distinguishing right- and left-handed states.
- In knot theory and fluid mechanics, the linking or twisting of closed curves or vortex lines.
"The drug altered the helicity of the DNA and prevented the replication machinery from functioning properly."
"Changes in temperature can affect the helicity of a short DNA duplex."
"The particle's helicity indicates whether its angular momentum is aligned or opposed to its direction of motion."
The plural is grammatical but uncommon; writers often discuss the helicity of individual molecules or structures.
"The helicities of the two folded molecules differed considerably."
DNA’s famous twist has a name: helicity.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does helicity come from?
The English word helicity was formed from helix with the noun-forming suffix -icity. Helix was borrowed into Latin from Greek helix, meaning “spiral,” and is associated with Greek helikos, referring to spiraling. The same root appears in English words such as helical, helicoid, and helicene.
How helicity is actually used
This is formal technical vocabulary, used chiefly in molecular biology, biophysics, particle physics, and related fields. In molecular biology, it describes structural twisting rather than the molecule as a whole. There is no significant British-versus-US distinction.
Easily confused with helicity
A helix is the spiral form or structure itself, whereas helicity is the measurable degree of twisting or helical character associated with a structure.