An atom or group of atoms (with pendant atoms or groups, if any) comprising a part of the essential structure of a @M03667@, an @O04286@, a @B00682@ or a @C00946@.
PAC, 1996, 68
, 2287. (Glossary of basic terms in polymer science (IUPAC Recommendations 1996)
) on page 2291 [Terms