diads

in polymers
https://doi.org/10.1351/goldbook.D01662
See: constitutional sequence (in polymers)
Source:
PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2299 (https://doi.org/10.1351/pac199668122287)