The whole or part of a chain comprising one or more species of constitutional unit(s) in defined sequence.
Constitutional sequences comprising two constitutional units are termed diads, those comprising three constitutional units triads, and so on. In order of increasing @ST06775@ lengths they are called tetrads, pentads, hexads, heptads, octads, nonads, decads, undecads, etc.
PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2299 (https://doi.org/10.1351/pac199668122287)