constitutional repeating unit

in polymers
https://doi.org/10.1351/goldbook.C01286
The smallest @C01288@ the repetition of which constitutes a @R05247@, a @R05248@, a @R05244@ or a regular @C00946@.
Source:
PAC, 1996, 68, 2287. (Glossary of basic terms in polymer science (IUPAC Recommendations 1996)) on page 2291 [Terms] [Paper]