Title: constitutional unit
Long Title: IUPAC Gold Book - constitutional unit
DOI: 10.1351/goldbook.C01288
Status: current

Definition
An atom or group of atoms (with pendant atoms or groups, if any) comprising a part of the essential structure of a macromolecule, an oligomer molecule, a block or a chain.

Related Terms
- block: https://goldbook.iupac.org//terms/view/B00682
- chain: https://goldbook.iupac.org//terms/view/C00946
- macromolecule: https://goldbook.iupac.org//terms/view/M03667
- oligomer molecule: https://goldbook.iupac.org//terms/view/O04286

Source
- PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2291 (https://doi.org/10.1351/pac199668122287)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/C01288/html
- json: https://goldbook.iupac.org/terms/view/C01288/json
- xml: https://goldbook.iupac.org/terms/view/C01288/xml

Citation: Citation: 'constitutional unit' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C01288
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-04-18T13:28:04+00:00