Term: angle strain https://doi.org/10.1351/goldbook.A00349 Definition: Strain due to a departure in bond angle from 'normal' values. The term is often used in the context of non-aromatic cyclic compounds in which the internal angles differ from the regular tetrahedral angle of 109° 28′; in this sense angle strain is also known as Baeyer strain. Related Terms: 1) strain (http://doi.org/10.1351/goldbook.S06037-1). 2) angle (http://doi.org/10.1351/goldbook.A00346). 3) baeyer strain (http://doi.org/10.1351/goldbook.B00586). 4) strain (http://doi.org/10.1351/goldbook.S06037-2). Source: PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2198 (https://doi.org/10.1351/pac199668122193) Citation: 'angle strain' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00349 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. 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.