worm-like chain

in polymers
Also contains definition of: Porod–Kratky chain in polymers
A hypothetical linear macromolecule consisting of an infinitely thin chain of continuous curvature; the direction of curvature at any point is random. The model describes the whole spectrum of chains with different degrees of chain stiffness from rigid rods to random coils, and is particularly useful for representing stiff chains. In the literature this chain is sometimes referred to as a Porod–Kratky chain. Synonymous with continuously curved chain.
Purple Book, 1st ed., p. 51 (http://old.iupac.org/publications/books/author/metanomski.html)