In polymer systems, the general definition () holds; the elementary constituents are now the monomers making up the chains. However, the structure factor being a measure of the correlation between particle positions, one can reasonably expect that this correlation will be different for monomers belonging to the same chain or to different chains.
Let us assume that the volume  contains  identical molecules, each composed of  monomers, such that  ( is also known as the degree of polymerization). We can rewrite () as:
where indices  label the different molecules and  the different monomers along each molecule. On the right-hand side we separated intramolecular () and intermolecular () terms. Using the equivalence of the chains, () can be simplified:
where  is the single-chain structure factor.