subchain

of a polymer
https://doi.org/10.1351/goldbook.S06065
An arbitrarily chosen contiguous sequence of constitutional units in a chain.
Note:
The term 'subchain' may be used to define designated subsets of the constitutional units in a chain.
Source:
PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2293 (https://doi.org/10.1351/pac199668122287)